BUG: directory information spoils "wmake -show-cxx" (fixes #1799)

- the various information queries MUST be executed with
  the '--no-print-directory' or risk polluting values
  in the information queries.

  This is mostly seen with the 'canCompile' test for tutorials running
  in parallel.

ENH: add wmake '-show-path-c', '-show-path-cxx' as per 1912 and later