add git-has-changes back to common-tools.sh it's used in newlib headers handling in build.sh, but apparently doesn't break the build (it just causes unnecessary cleaning)
add git-has-changes back to common-tools.sh
it's used in newlib headers handling in build.sh, but apparently doesn't
break the build (it just causes unnecessary cleaning)

R=jvoung@chromium.org
BUG=

Review URL: https://chromiumcodereview.appspot.com/10829345

git-svn-id: 721b910a23eff8a86f00c8fd261a7587cddf18f8@9482 fcba33aa-ac0c-11dd-b9e7-8d5594d729c2

nacl-webkit/native_client,sbc100/native_client,nacl-webkit/native_client,nacl-webkit/native_client,nacl-webkit/native_client,nacl-webkit/native_client,sbc100/native_client,sbc100/native_client,sbc100/native_client,sbc100/native_client,sbc100/native_client