lua: enhanced lua.conf to install lua.pc

lua/lua/lua.conf

@@ -45,6 +45,7 @@ lua_postmake() {
 	mkdir -p "$root$luadatadir"
 
 	cp -v doc/* "$root$docdir"
+	sed -e "s:/usr/local:/$prefix:" etc/lua.pc > "$root$libdir/pkgconfig/"
 }
 
 hook_add postmake 3 lua_postmake