Return zero from extract_file with local source file

The call to bsdtar to check if a file needs extracted returns 1 if it does
not.  We then propegate this return value accidentally which can cause
makepkg to report an error later on.  Explicitly return 0 in this case.

Signed-off-by: Allan McRae <allan@archlinux.org>

scripts/makepkg.sh.in

@@ -419,7 +419,7 @@ extract_file() {
 			if bsdtar -tf "$file" -q '*' &>/dev/null; then
 				cmd="bsdtar"
 			else
-				return
+				return 0
 			fi ;;
 	esac