test-unit-php and test-unit-ruby exited 0 whenever the interpreter or the
vendor tree was missing, so both suites were silently absent from every
gate. They now provision their toolchain through install-php/install-ruby
and fail loudly when that is impossible.
The three ensure_*_present helpers collapse into ensure_command_present
in system_pkg, and the ruby runner rejects an empty suite because
minitest reports success when nothing was required.
