Merge branch 'check_test_coverage' of https://github.com/cgoesche/util-linux-fork

* 'check_test_coverage' of https://github.com/cgoesche/util-linux-fork:
  tests: search for all executable scripts in test subdirs
  build-sys: add a target for tools/testcoverage.sh
  tools: (get-options.sh) refine regex for unsupported programs to avoid false positives
  tools: expand relative paths provided by $top_srcdir for robustness
  tools: helper script to generate a test coverage report
  tools: (get-options.sh) ensure functionality for out-of-tree builds