It now handles adding .bp files and changing globs.
In order to do this, depfiles are now written separately from RunBlueprint.
This is necessary due to the confluence of a number of seemingly
unrelated factors:
1. The glob filelist dependencies are discovered in globSingleton
2. Singletons need to be registered because otherwise singleton module
types panic
3. Singletons don't work because they require mutators bp2build does not
run
Due to (1), we would need to run the glob singleton. However, due to (2)
and (3), we can't run singletons and have to run Blueprint with
StopBeforeGeneratingBuildActions, which is when the build actions
writing glob files would be generated. So what happens is:
1. When bp2build is run, the glob singleton is disabled
2. At the end of bp2build, the list of glob files is artifically added
to the depfile of the workspace marker file
3. When build.ninja is generated, the Ninja file containing the glob
list file is written by the now-active glob singleton
Test: Presubmits.
Change-Id: I3c5898d8c57c554a93520276c64a952afc912dbe
d518e1a407