Merge branch 'jc/unit-tests-make-relative-fix'

The mechanism to report the filename in the source code, used by the unit-test machinery, assumed that the compiler expanded __FILE__ to the path to the source given to the $(CC), but some compilers give full path, breaking the output. This has been corrected. * jc/unit-tests-make-relative-fix: unit-tests: do show relative file paths on non-Windows, too