Test suite: Add extensive fuzzing tests to all coreutils

[chorman0773]

Presently the coreutils are only tested for correctness, and only in limited ways.
There are no tests for segmentation faults (aside from some cleverly named tests), or for buffer overrun vulnerabilities. An extensive fuzzer should be run over all lc-coreutils. Additionally, all coreutils should be run automatically with valgrind, failing if any memory errors are detected.

Progress:

• Valgrind tests for all coreutils
  • hashfile
  • true
  • false
  • echo
  • chmod-parse
  • chmod
  • mkdir
  • mknod
  • mkfifo
  • which
  • yes
  • link
  • nohup
  • basename
  • dirname
• Fuzzing for all coreutils
  • hashfile
  • true
  • false
  • echo
  • chmod-parse
  • chmod
  • mkdir
  • mknod
  • mkfifo
  • which
  • yes
  • link
  • nohup
  • basename
  • dirname

[chorman0773]

valgrind testing is now enabled for hashfile, with CI coverage.

All valgrind tests are only enabled by the config option LCNIX_COREUTILS_VALGRIND_TESTS.