Resolution of source file for failed tests is invalid

When a test fails, it shows the failure location (using _FILE and LINE_)

This information is used by the parser to link to the source file.

Since _FILE_ is relative, a base directory is needed for resolving it to a full path.

The base directory that is used is the application path. This is wrong both for shadow and in-source build (at least on Windows).

The executable is placed in debug/test.exe, while the Makefile is one directory above it, and the reference is to ../test/test.cpp for shadow build or just test.cpp for in-source.

The base directory should be the directory from which make was executed.