abuild: run subpackage split functions in a subshell

so subfunctions don't overwrite the global variables like depends, pkgdesc etc.

abuild.in

@@ -659,9 +659,9 @@ prepare_subpackages() {
 		# call abuild recursively, setting subpkg{dir,name}
 		msg "Running split function $func..."
 		local dir="$pkgbasedir/${i%:*}" name="${i%:*}"
-		subpkgdir="$dir" subpkgname="$name" \
-			$0 $func prepare_package || return 1
-		postcheck "$dir" "$name" || return 1
+		( subpkgdir="$dir" subpkgname="$name" \
+			$0 $func prepare_package \
+			&& postcheck "$dir" "$name" ) || return 1
 	done
 	postcheck "$pkgdir" "$pkgname" || return 1
 	# post check for /usr/share/locale