release.sh: use cache src on release builds

use what's in cache/clone/ from the main directory

this speeds up the build process

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

include/release.sh

@@ -59,6 +59,9 @@ prep_release()
 	(
 		if [ "$1" != "tarball" ]; then
 			x_ cd "$rsrc"
+			if [ ! -e "cache" ]; then
+				x_ ln -s "$XBMK_CACHE" "cache"
+			fi
 		fi
 
 		prep_release_$1
@@ -94,8 +97,8 @@ prep_release_tarball()
 	    --abbrev-commit > "$rsrc/CHANGELOG" || \
 	    err "can't create '$rsrc/CHANGELOG'" "prep_release_tarball" "$@" 
 
-	x_ rm -f "$rsrc/lock"
-	x_ rm -Rf "$rsrc/cache" "$rsrc/xbmkwd"
+	x_ rm -f "$rsrc/lock" "$rsrc/cache"
+	x_ rm -Rf "$rsrc/xbmkwd"
 
 	(
 		x_ cd "${rsrc%/*}"