Minion: Use minion's build system not build.rs to build libminion, and CI tweaks

[niklasdewally]

#1

Chris Jefferson has added support for building Minion as a library through its own build system: minion/minion#6.

This PR removes the code in build.rs that builds the libminion.a library, and instead calls minion's build system to do this for us.

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I have also implemented CI caching as per #4.

The primary issue was the time needed to build minion. Therefore, minion's build directory is cached so that make can do proper incremental builds.

Also, build.rs should now not run at all unless it or vendor code changes.

[niklasdewally]

[ozgurakgun]

I think this works for minion caching, yes! I was thinking it would be easier to give hashFiles more files.

Oh also, for restore-keys I think you can just say ${{ runner.os }}. It picks the newest matching cache anyway.

Merging like this, we can always improve it later & if needed.

[niklasdewally]

Oh also, for restore-keys I think you can just say ${{ runner.os }}. It picks the newest matching cache anyway.

When minion updates (especially when new files are added), a clean build is sometimes needed for it to work properly. Requiring an exact match for minion in the cache would force a clean build in CI when needed.

(build.rs does not re-run ./configure for minion if the build directory already exists, as ./configure effectively forces a clean build.)

[niklasdewally]

@ozgurakgun is this ready for merge?