Prevent our libstdc++.dylib from having a runtime dependency on
/usr/lib/libstdc++.dylib.  This is caused by the implicit -lstdc++
passed by g++ when it links libstdc++.dylib.  Adding "-nostdlib" to
the g++ invocation prevents this.

diff -ru -x '*~' libstdcxx-39-orig/libstdcxx/libstdc++-v3/src/Makefile.in libstdcxx-39/libstdcxx/libstdc++-v3/src/Makefile.in
--- x/libstdcxx/libstdc++-v3/src/Makefile.in	2006-10-16 21:08:22.000000000 +0200
+++ y/libstdcxx/libstdc++-v3/src/Makefile.in	2012-02-17 18:44:05.210570590 +0100
@@ -388,7 +388,7 @@
 
 libstdc___la_DEPENDENCIES = ${version_dep} $(libstdc___la_LIBADD)
 libstdc___la_LDFLAGS = \
-	-version-info $(libtool_VERSION) ${version_arg} -lm 
+	-version-info $(libtool_VERSION) ${version_arg} -lm -Wc,-nostdlib
 
 
 # Use special rules for the deprecated source files so that they find