Implement two-pass script parsing.

In preparation of future work. The NDK build script will now parse all
Android.mk and record LOCAL_XXX variables in the modules database.

After all parsing is done, it will populate the dependency graph with
targets and commands. This will allow us to implement "exported" module
variables like LOCAL_EXPORT_CFLAGS and others in a reliable way.

Change-Id: If1eb4ce68b62b5dfa146520a77cbcad401272428
9 files changed