xbps-src: multiple improvements for -B and run_func.

* run_func now errors out by itself if the function returned any error.
* if -B flag is enabled and binpkg already exists, skip updating local
  repo pkg-index.

xbps-src/shutils/extract_funcs.sh

@@ -40,6 +40,11 @@ extract_distfiles()
 	#
 	[ -n "$pkg" -a -z "$pkgname" ] && return 1
 
+	if [ -n "$revision" ]; then
+		lver="${version}_${revision}"
+	else
+		lver="${version}"
+	fi
 	#
 	# If noextract is set, do a "fake extraction".
 	#