abuild: support for building simple tar.gz files of target

When building with crosscompile to bootstrap a new target it might
be handy to not include the dependencies etc.

abuild.in

@@ -317,6 +317,12 @@ build() {
 	:
 }
 
+# generate a simple tar.gz package of pkgdir
+targz() {
+	cd "$pkgdir" || return 1
+	tar -czf "$PKGDEST"/$pkgname-$pkgver-r$pkgrel.tar.gz *
+}
+
 get_split_func() {
 	# get the 'func' from "sub-pkg:func"
 	local func=${1##*:}