Don't use recursion in the script. The Python's os.walk() already
lists all files in subdirectories and using recursion only caused
tests to be found twice. Also handle the case the project file
defines binary path with DESTDIR define.
Improve the runner script to run only tests whose binary file
exists. Tests with inexistant binary file are not counted into
test counts in the summary.
Add the MIT license header. I'm now maintaining this script in
external repository with MIT license. So I can use the script
in other projects too.