Add build test runner: b-test.

Test runner can be used to do build testing. The main intention is to
provide a simple and robust way to capture build commands.

For details please check the documentation.

Change-Id: Icab22320a86dcfdb882a36c1c8c2a3380c40d30c
Signed-off-by: Gyorgy Szing <gyorgy.szing@arm.com>
8 files changed