Add per-directory build targets

Build a map of blueprint directory to modules built from that
directory, and then add phony rules to build.ninja that emulate
the behavior of mma in the current build system.

Also fixes checkbuild to depend on checkbuild files and installable
files, but not installed files.

Change-Id: I8bad6e93387940df7439dbd4554f6d79f924c65f
6 files changed