Some more background information:
Machine: Linux xxxx.xxxx.com 2.6.18-53.1.4.el5 #1 SMP Wed Nov 14 10:37:27 EST
2007 x86_64 x86_64 x86_64 GNU/Linux

I have not found official Apache documentation on how to build the server in
64bit. I'm not even sure if that's a supported platform.

Here is what I have done:

[testuser@testserver1 httpd-2.2.8]$ export CFLAGS=-m64
[testuser@testserver1 httpd-2.2.8]$ make
Making all in srclib
make[1]: Entering directory `/home/testuser/webservers/httpd-2.2.8/srclib'
Making all in apr
make[2]: Entering directory `/home/testuser/webservers/httpd-2.2.8/srclib/apr'
make[3]: Entering directory `/home/testuser/webservers/httpd-2.2.8/srclib/apr'
make[3]: Nothing to be done for `local-all'.
make[3]: Leaving directory `/home/testuser/webservers/httpd-2.2.8/srclib/apr'
make[2]: Leaving directory `/home/testuser/webservers/httpd-2.2.8/srclib/apr'
Making all in apr-util
make[2]: Entering directory
`/home/testuser/webservers/httpd-2.2.8/srclib/apr-util'
make[3]: Entering directory
`/home/testuser/webservers/httpd-2.2.8/srclib/apr-util'
make[3]: Nothing to be done for `local-all'.
make[3]: Leaving directory
`/home/testuser/webservers/httpd-2.2.8/srclib/apr-util'
make[2]: Leaving directory
`/home/testuser/webservers/httpd-2.2.8/srclib/apr-util'
Making all in pcre
make[2]: Entering directory `/home/testuser/webservers/httpd-2.2.8/srclib/pcre'
make[3]: Entering directory `/home/testuser/webservers/httpd-2.2.8/srclib/pcre'
make[3]: Nothing to be done for `local-all'.
make[3]: Leaving directory `/home/testuser/webservers/httpd-2.2.8/srclib/pcre'
make[2]: Leaving directory `/home/testuser/webservers/httpd-2.2.8/srclib/pcre'
make[1]: Leaving directory `/home/testuser/webservers/httpd-2.2.8/srclib'
Making all in os
make[1]: Entering directory `/home/testuser/webservers/httpd-2.2.8/os'
Making all in unix
make[2]: Entering directory `/home/testuser/webservers/httpd-2.2.8/os/unix'
make[3]: Entering directory `/home/testuser/webservers/httpd-2.2.8/os/unix'
make[3]: Nothing to be done for `local-all'.
make[3]: Leaving directory `/home/testuser/webservers/httpd-2.2.8/os/unix'
make[2]: Leaving directory `/home/testuser/webservers/httpd-2.2.8/os/unix'
make[1]: Leaving directory `/home/testuser/webservers/httpd-2.2.8/os'
Making all in server
make[1]: Entering directory `/home/testuser/webservers/httpd-2.2.8/server'
Making all in mpm
make[2]: Entering directory `/home/testuser/webservers/httpd-2.2.8/server/mpm'
Making all in prefork
make[3]: Entering directory
`/home/testuser/webservers/httpd-2.2.8/server/mpm/prefork'
make[4]: Entering directory
`/home/testuser/webservers/httpd-2.2.8/server/mpm/prefork'
make[4]: Nothing to be done for `local-all'.
make[4]: Leaving directory
`/home/testuser/webservers/httpd-2.2.8/server/mpm/prefork'
make[3]: Leaving directory
`/home/testuser/webservers/httpd-2.2.8/server/mpm/prefork'
make[2]: Leaving directory `/home/testuser/webservers/httpd-2.2.8/server/mpm'
make[2]: Entering directory `/home/testuser/webservers/httpd-2.2.8/server'
make[2]: Leaving directory `/home/testuser/webservers/httpd-2.2.8/server'
make[1]: Leaving directory `/home/testuser/webservers/httpd-2.2.8/server'
Making all in modules
make[1]: Entering directory `/home/testuser/webservers/httpd-2.2.8/modules'
Making all in aaa
make[2]: Entering directory `/home/testuser/webservers/httpd-2.2.8/modules/aaa'
make[3]: Entering directory `/home/testuser/webservers/httpd-2.2.8/modules/aaa'
make[3]: Nothing to be done for `local-all'.
make[3]: Leaving directory `/home/testuser/webservers/httpd-2.2.8/modules/aaa'
make[2]: Leaving directory `/home/testuser/webservers/httpd-2.2.8/modules/aaa'
Making all in filters
make[2]: Entering directory
`/home/testuser/webservers/httpd-2.2.8/modules/filters'
make[3]: Entering directory
`/home/testuser/webservers/httpd-2.2.8/modules/filters'
make[3]: Nothing to be done for `local-all'.
make[3]: Leaving directory
`/home/testuser/webservers/httpd-2.2.8/modules/filters'
make[2]: Leaving directory
`/home/testuser/webservers/httpd-2.2.8/modules/filters'
Making all in loggers
make[2]: Entering directory
`/home/testuser/webservers/httpd-2.2.8/modules/loggers'
make[3]: Entering directory
`/home/testuser/webservers/httpd-2.2.8/modules/loggers'
make[3]: Nothing to be done for `local-all'.
make[3]: Leaving directory
`/home/testuser/webservers/httpd-2.2.8/modules/loggers'
make[2]: Leaving directory
`/home/testuser/webservers/httpd-2.2.8/modules/loggers'
Making all in metadata
make[2]: Entering directory
`/home/testuser/webservers/httpd-2.2.8/modules/metadata'
make[3]: Entering directory
`/home/testuser/webservers/httpd-2.2.8/modules/metadata'
make[3]: Nothing to be done for `local-all'.
make[3]: Leaving directory
`/home/testuser/webservers/httpd-2.2.8/modules/metadata'
make[2]: Leaving directory
`/home/testuser/webservers/httpd-2.2.8/modules/metadata'
Making all in ssl
make[2]: Entering directory `/home/testuser/webservers/httpd-2.2.8/modules/ssl'
make[3]: Entering directory `/home/testuser/webservers/httpd-2.2.8/modules/ssl'
make[3]: Nothing to be done for `local-all'.
make[3]: Leaving directory `/home/testuser/webservers/httpd-2.2.8/modules/ssl'
make[2]: Leaving directory `/home/testuser/webservers/httpd-2.2.8/modules/ssl'
Making all in http
make[2]: Entering directory
`/home/testuser/webservers/httpd-2.2.8/modules/http'
make[3]: Entering directory
`/home/testuser/webservers/httpd-2.2.8/modules/http'
make[3]: Nothing to be done for `local-all'.
make[3]: Leaving directory `/home/testuser/webservers/httpd-2.2.8/modules/http'
make[2]: Leaving directory `/home/testuser/webservers/httpd-2.2.8/modules/http'
Making all in generators
make[2]: Entering directory
`/home/testuser/webservers/httpd-2.2.8/modules/generators'
make[3]: Entering directory
`/home/testuser/webservers/httpd-2.2.8/modules/generators'
make[3]: Nothing to be done for `local-all'.
make[3]: Leaving directory
`/home/testuser/webservers/httpd-2.2.8/modules/generators'
make[2]: Leaving directory
`/home/testuser/webservers/httpd-2.2.8/modules/generators'
Making all in mappers
make[2]: Entering directory
`/home/testuser/webservers/httpd-2.2.8/modules/mappers'
make[3]: Entering directory
`/home/testuser/webservers/httpd-2.2.8/modules/mappers'
make[3]: Nothing to be done for `local-all'.
make[3]: Leaving directory
`/home/testuser/webservers/httpd-2.2.8/modules/mappers'
make[2]: Leaving directory
`/home/testuser/webservers/httpd-2.2.8/modules/mappers'
make[1]: Leaving directory `/home/testuser/webservers/httpd-2.2.8/modules'
Making all in support
make[1]: Entering directory `/home/testuser/webservers/httpd-2.2.8/support'
make[2]: Entering directory `/home/testuser/webservers/httpd-2.2.8/support'
make[2]: Nothing to be done for `local-all'.
make[2]: Leaving directory `/home/testuser/webservers/httpd-2.2.8/support'
make[1]: Leaving directory `/home/testuser/webservers/httpd-2.2.8/support'
make[1]: Entering directory `/home/testuser/webservers/httpd-2.2.8'
gcc -g -O2 -pthread    -DLINUX=2 -D_REENTRANT -D_GNU_SOURCE  
-I/home/testuser/webservers/httpd-2.2.8/srclib/pcre -I.
-I/home/testuser/webservers/httpd-2.2.8/os/unix
-I/home/testuser/webservers/httpd-2.2.8/server/mpm/prefork
-I/home/testuser/webservers/httpd-2.2.8/modules/http
-I/home/testuser/webservers/httpd-2.2.8/modules/filters
-I/home/testuser/webservers/httpd-2.2.8/modules/proxy
-I/home/testuser/webservers/httpd-2.2.8/include
-I/home/testuser/webservers/httpd-2.2.8/modules/generators
-I/home/testuser/webservers/httpd-2.2.8/modules/mappers
-I/home/testuser/webservers/httpd-2.2.8/modules/database
-I/home/testuser/webservers/httpd-2.2.8/srclib/apr/include
-I/home/testuser/webservers/httpd-2.2.8/srclib/apr-util/include
-I/home/testuser/webservers/httpd-2.2.8/modules/proxy/../generators
-I/usr/kerberos/include -I/home/testuser/webservers/httpd-2.2.8/modules/ssl
-I/home/testuser/webservers/httpd-2.2.8/modules/dav/main  -c
/home/testuser/webservers/httpd-2.2.8/server/buildmark.c
/home/testuser/webservers/httpd-2.2.8/srclib/apr/libtool --silent --mode=link
gcc -g -O2 -pthread        -o httpd  modules.lo buildmark.o -export-dynamic
server/libmain.la modules/aaa/libmod_authn_file.la
modules/aaa/libmod_authn_default.la modules/aaa/libmod_authz_host.la
modules/aaa/libmod_authz_groupfile.la modules/aaa/libmod_authz_user.la
modules/aaa/libmod_authz_default.la modules/aaa/libmod_auth_basic.la
modules/filters/libmod_include.la modules/filters/libmod_filter.la
modules/loggers/libmod_log_config.la modules/metadata/libmod_env.la
modules/metadata/libmod_setenvif.la modules/ssl/libmod_ssl.la
modules/http/libmod_http.la modules/http/libmod_mime.la
modules/generators/libmod_status.la modules/generators/libmod_autoindex.la
modules/generators/libmod_asis.la modules/generators/libmod_cgi.la
modules/mappers/libmod_negotiation.la modules/mappers/libmod_dir.la
modules/mappers/libmod_actions.la modules/mappers/libmod_userdir.la
modules/mappers/libmod_alias.la modules/mappers/libmod_so.la
server/mpm/prefork/libprefork.la os/unix/libos.la -lm
/home/testuser/webservers/httpd-2.2.8/srclib/pcre/libpcre.la
/home/testuser/webservers/httpd-2.2.8/srclib/apr-util/libaprutil-1.la -lsqlite3
-lexpat /home/testuser/webservers/httpd-2.2.8/srclib/apr/libapr-1.la -luuid
-lrt -lcrypt -lpthread -ldl
/home/testuser/webservers/httpd-2.2.8/srclib/apr-util/.libs/libaprutil-1.so:
could not read symbols: File in wrong format
collect2: ld returned 1 exit status
make[1]: *** [httpd] Error 1
make[1]: Leaving directory `/home/testuser/webservers/httpd-2.2.8'
make: *** [all-recursive] Error 1