release.sh: fix broken release lock file handling

we need to copy the main lock file, rather than creating
a new, empty one. this is because the new lock file
handling requires it, and the release lock file will
be used during release builds.

Signed-off-by: Leah Rowe <leah@libreboot.org>

include/release.sh

@@ -43,7 +43,7 @@ release()
 
 prep_release()
 {
-	x_ touch "$rsrc/lock"
+	x_ cp "$xbmklock" "$rsrc/lock"
 	(
 	[ "$1" = "tarball" ] || x_ cd "$rsrc"
 	prep_release_$1