[PATCH, PR 66521,part 2] Fix warnings on darwin when bootstrapping with vtable verification enabled

[Caroline Tice]

When bootstrapping on darwin with vtable verificaiton enabled,
libstdc++ is giving  a lot of warnings due to a flag in
VTV_CXXLINKFLAGS that has a slightly different format for darwin than
for linux.  This patch (actually contributed by Eric Gallager) fixes
the problem.

I have tested this patch by bootstrapping and running the entire
testsuite with no regressions.  Is this OK to commit?

-- Caroline Tice
cmt...@google.com

Index: libstdc++-v3/acinclude.m4
===================================================================
--- libstdc++-v3/acinclude.m4	(revision 226760)
+++ libstdc++-v3/acinclude.m4	(working copy)
@@ -2325,14 +2325,19 @@
     case ${target_os} in
       cygwin*|mingw32*)
         VTV_CXXFLAGS="-fvtable-verify=std -Wl,-lvtv,-u_vtable_map_vars_start,-u_vtable_map_vars_end"
+        VTV_CXXLINKFLAGS="-L${toplevel_builddir}/libvtv/.libs -Wl,--rpath -Wl,${toplevel_builddir}/libvtv/.libs"
         vtv_cygmin=yes
         ;;
+      darwin*)
+        VTV_CXXFLAGS="-fvtable-verify=std -Wl,-u,_vtable_map_vars_start -Wl,-u,_vtable_map_vars_end"
+        VTV_CXXLINKFLAGS="-L${toplevel_builddir}/libvtv/.libs -Wl,-rpath,${toplevel_builddir}/libvtv/.libs"
+        ;;
       *)
         VTV_CXXFLAGS="-fvtable-verify=std -Wl,-u_vtable_map_vars_start,-u_vtable_map_vars_end"
+        VTV_CXXLINKFLAGS="-L${toplevel_builddir}/libvtv/.libs -Wl,--rpath -Wl,${toplevel_builddir}/libvtv/.libs"
         ;;
     esac
     VTV_PCH_CXXFLAGS="-fvtable-verify=std"
-    VTV_CXXLINKFLAGS="-L${toplevel_builddir}/libvtv/.libs -Wl,--rpath -Wl,${toplevel_builddir}/libvtv/.libs"		
   else
     VTV_CXXFLAGS= 
     VTV_PCH_CXXFLAGS=
Index: libstdc++-v3/configure
===================================================================
--- libstdc++-v3/configure	(revision 226760)
+++ libstdc++-v3/configure	(working copy)
@@ -17433,14 +17433,19 @@
     case ${target_os} in
       cygwin*|mingw32*)
         VTV_CXXFLAGS="-fvtable-verify=std -Wl,-lvtv,-u_vtable_map_vars_start,-u_vtable_map_vars_end"
+        VTV_CXXLINKFLAGS="-L${toplevel_builddir}/libvtv/.libs -Wl,--rpath -Wl,${toplevel_builddir}/libvtv/.libs"
         vtv_cygmin=yes
         ;;
+      darwin*)
+        VTV_CXXFLAGS="-fvtable-verify=std -Wl,-u,_vtable_map_vars_start -Wl,-u,_vtable_map_vars_end"
+        VTV_CXXLINKFLAGS="-L${toplevel_builddir}/libvtv/.libs -Wl,-rpath,${toplevel_builddir}/libvtv/.libs"
+        ;;
       *)
         VTV_CXXFLAGS="-fvtable-verify=std -Wl,-u_vtable_map_vars_start,-u_vtable_map_vars_end"
+        VTV_CXXLINKFLAGS="-L${toplevel_builddir}/libvtv/.libs -Wl,--rpath -Wl,${toplevel_builddir}/libvtv/.libs"
         ;;
     esac
     VTV_PCH_CXXFLAGS="-fvtable-verify=std"
-    VTV_CXXLINKFLAGS="-L${toplevel_builddir}/libvtv/.libs -Wl,--rpath -Wl,${toplevel_builddir}/libvtv/.libs"
   else
     VTV_CXXFLAGS=
     VTV_PCH_CXXFLAGS=