genbuild_h.sh: Get current rev for git revision, not origin/master

Using origin/master as the git revision breaks reproducibility, giving
different values depending on when the code was pulled from the
repo at coreboot.org.  By using the current revision instead, we get
identical builds.

Change-Id: If4be6e048d6c8e417b8c074199745900ccd82b49
Signed-off-by: Martin Roth <martinroth@google.com>
Reviewed-on: https://review.coreboot.org/12807
Tested-by: build bot (Jenkins)
Reviewed-by: Zheng Bao <zheng.bao@amd.com>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>

util/genbuild_h/genbuild_h.sh

@@ -25,7 +25,7 @@ export TZ=UTC
 top=`dirname $0`/../..
 
 if [ -d "${top}/.git" -a -x "$(command -v git)" ]; then
-	GITREV=$(LANG= git log remotes/origin/master -1 --format=format:%h)
+	GITREV=$(LANG= git log -1 --format=format:%h)
 	TIMESOURCE=git
 	DATE=$(git log --pretty=format:%ct -1)
 else