Bug 707868 - factor setting of CC and CXX for mac os X. r=rail.

browser/config/mozconfigs/macosx64/debug

@@ -1,3 +1,5 @@
+. $topsrcdir/build/macosx/common
+
 ac_add_options --enable-debug
 ac_add_options --enable-trace-malloc
 ac_add_options --enable-accessibility

build/macosx/common

@@ -0,0 +1,2 @@
+CC=/usr/bin/gcc-4.2
+CXX=/usr/bin/g++-4.2

build/macosx/mozconfig.leopard

@@ -1,10 +1,4 @@
-if test -z "$CC" ; then
-   CC=gcc-4.2
-fi
-
-if test -z "$CXX" ; then
-   CXX=g++-4.2
-fi
+. $topsrcdir/build/macosx/common
 
 # Mac builds don't nomally have to be handled as cross
 # compilation, but some of the libraries on the bots

build/macosx/universal/mozconfig.common

@@ -45,6 +45,8 @@ ac_add_app_options x86_64 --target=x86_64-apple-darwin10
 ac_add_app_options i386 --with-macos-sdk=/Developer/SDKs/MacOSX10.5.sdk
 ac_add_app_options x86_64 --with-macos-sdk=/Developer/SDKs/MacOSX10.6.sdk
 
+. $topsrcdir/build/macosx/common
+
 # $MOZ_BUILD_APP is only defined when sourced by configure.  That's not a
 # problem, because the variables it affects only need to be set for
 # configure.
@@ -52,14 +54,6 @@ if test -n "$MOZ_BUILD_APP" ; then
 if test "$MOZ_BUILD_APP" = "i386" -o "$MOZ_BUILD_APP" = "x86_64"; then
   TARGET_CPU=$MOZ_BUILD_APP
 
-  if test -z "$CC" ; then
-     CC=gcc-4.2
-  fi
-
-  if test -z "$CXX" ; then
-     CXX=g++-4.2
-  fi
-
   # $HOST_CXX is presently unused.  $HOST_CC will only be used during a cross
   # compile.
   HOST_CC=$CC