Allow an optional supplemental commit message on builds

Change-Id: I8a9cd32b50121f6c02b78b1f97eb78d6946cd71e
Reviewed-on: https://swiftshader-review.googlesource.com/3476
Reviewed-by: Nicolas Capens <capn@google.com>
Tested-by: Greg Hartman <ghartman@google.com>
diff --git a/android_vendor_build.sh b/android_vendor_build.sh
index 7a7faac..68cae7b 100755
--- a/android_vendor_build.sh
+++ b/android_vendor_build.sh
@@ -101,6 +101,7 @@
   -m "${WARN} SwiftShader build as of:" \
   -m "    git hash: $( cd ${SOURCE_DIR}; git log -n1 | grep commit | head -1 | awk '{ print $2; }')" \
   -m "$(cd ${SOURCE_DIR}; git log -n1 | grep '^ *Change-Id:' | tail -1 | sed 's,-, ,')" \
-  -m "    At $(cd ${SOURCE_DIR}; git remote -v | grep ^origin | head -1 | awk '{ print $2; }')"
+  -m "    At $(cd ${SOURCE_DIR}; git remote -v | grep ^origin | head -1 | awk '{ print $2; }')" \
+  -m "$1"
 popd
 rm -rf ${SOURCE_DIR_LINKED}