Include signing/ from toplevel and default most packages to true.

- Include signing/ subdir in toplevel Makefile.
  Previously, we would build google_platform and google_signing as two
  separate builds, which was unnecessarily weird.  Build them both from the
  toplevel (requires a corresponding change in buildroot).

- Default most packages to on.  'make test' (outside buildroot) was not
  running tests for a bunch of packages where it could have been.
  (Packages which are off by default are ones which seem hopeless to try
  to build without extra packages available.)

- Some missing .gitignore entries.

- $(EXTRACFLAGS) so we can build protobuf-using libraries for the host.

Change-Id: I7d0d135edbbe900d3b7c63afed41d3ec65084ccf
15 files changed