Revert "xbps-src: when all deps have been processed exit directly."

This reverts commit 9bf1ba5f88.

I still think the behaviour I observed was related to something else.

common/xbps-src/shutils/pkgtarget.sh

@@ -114,7 +114,7 @@ install_pkg() {
         # Package built successfully. Exit directly due to nested install_pkg
         # and install_pkg_deps functions.
         remove_cross_pkg $cross
-        exit 0
+        return 0
     fi
 }