http://issues.apache.org/jira/browse/STDCXX-191

Index: etc/config/gcc.config
===================================================================
--- etc/config/gcc.config       (revision 410400)
+++ etc/config/gcc.config       (working copy)
@@ -157,8 +157,11 @@
        MULTI_CPPFLAGS_POSIX = -D_REENTRANT
        MULTI_LDFLAGS_POSIX   = -lpthread
      else
-      MULTI_CPPFLAGS_POSIX = -pthread
-      MULTI_LDFLAGS_POSIX  = -pthread
+      # option doesn't exist in Darwin gcc
+      ifneq ($(OSNAME),Darwin)
+        MULTI_CPPFLAGS_POSIX = -pthread
+        MULTI_LDFLAGS_POSIX  = -pthread
+      endif
      endif
    endif
else