Clean up files' dependencies on phony targets.

Module names are phony targets, which make always sees as obsolete,
so a nothing-to-do build won't do nothing.
Also file target $(DEFAULT_TEST_PLAN) was never created in its rule.
Here it's fixed with a stamp file.

Bug:9761012
Change-Id: Ic82df70cc22643d902017b5bec1022404d9bbfce