Tweak how we set GK_HEAD_DIR and report the value in test_make

This is an important step towards being able to do things such as build a single test from within the test directory. Without this change we must invoke make from the top level of the repository in order for our makefile to function as expected.

Also adds local_test target in tests_common which enables building tests by running make in the local test directory.

Moves processName into utils so that the tests get access to this method (fixes Linking messages with empty information)