bad changes to object building recently

[David Miller]

I don't know what has caused this but I am hitting two big problems
which are severely effecting my daily workflow:

1) Something is grinding like crazy when just building a single
   object like "make path/to/foo.o", it looks like make is churning
   on lots of work.

   This used to be instantaneous and is essential for my build sanity
   checking when I apply networking patches.

2) You no longer can do a "make path/to/foo.o" to force an object file
   to be built outside of your current config.  This is also essential
   for my workflow, I can force build objects only enable'able on
   other platforms and it works %95 of the time for basic build sanity
   checking.

Someone please track down these problems and fix them.

Thank you.