cmake, autotools, meson: Remove deprecated variables

[gtristan]

Fixes #34.

[nanonyme]

Your cache key values are wrong

[gtristan]

It’s worse than that.

the cache key values are correct, but wrong when running with newer dependencies in tox.

I’ve debugged this and narrowed it down to an issue in variable substitution, and I’ll open a separate issue for that.

[gtristan]

It’s worse than that.

the cache key values are correct, but wrong when running with newer dependencies in tox.

I’ve debugged this and narrowed it down to an issue in variable substitution, and I’ll open a separate issue for that.

Whew, thank god it's not that bad.

I checked:

• Is it ujson that is formatting the make variable as "make" instead of "make " ?
  • Ruled out ujson version as generating different output
• Is it variable substitution that is ignoring the %{make-args} variable for some reason ? maybe because it is initially "" ?
  • After lots of debugging here, could not find a bug in _variables.pyx
  • Determined that the make variable is initially loaded from autotools.yaml as simply make instead of make %{make-args}
• Debugging yaml loading for a while, reducing test case, adding debug tracing

All of this time wasted, finally I find that the problem is in the project.conf of the cache key test.

This project.conf loads the plugins via the pip origin, works fine in CI, however, in the normal case when you have a stale buildstream-plugins package locally installed from months ago when %{make-args} didn't exist, it is completely incorrect when for running python3 -m buildstream._testing._update_cachekeys to update the cache keys.