init.sh: create separate lock in release dirs

this removes the current hackiness, preventing
build errors since xbtmp is now based on xbmkpwd,
which changes when we're in the release dir.

XBMK_RELEASE is still set accordingly, so this
will still work the same way.

this is also cleaner in general.

XBMK_CACHE is still the same, so the release work
directory still re-uses files from the main work
directory, rather than re-creating them.

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

include/release.sh

@@ -42,7 +42,6 @@ release()
 
 prep_release()
 {
-	x_ cp "$xbmklock" "$rsrc/lock"
 	(
 	[ "$1" = "tarball" ] || x_ cd "$rsrc"
 	prep_release_$1