Remove test_built_uses_configured_ninja_outside_path per review: it copied
whatever ninja was on PATH and asserted one existed, so the suite failed on
exactly the setup this PR fixes. The rewritten tests already verify the
configured CMAKE_MAKE_PROGRAM is the program that runs; the suite now passes
with and without Ninja on PATH on Windows and Linux.
tools/check_test_registration.py invoked bare ninja from PATH, so the audit failed with FileNotFoundError when the configured Ninja lived outside PATH. Read CMAKE_MAKE_PROGRAM from the build directory CMakeCache.txt and fail honestly when it is missing. Adapt the mocked built tests to a configured build and add a regression that runs a real Ninja from a path with spaces outside PATH.
Rujul Talekar
ArjenS-LA
MrMha
Привалов Александр Владимирович