xbps-src: add sccache support

[Logarithmus]

This PR adds support for using sccache when building cargo crates with xbps-src, just like ccache.
Unfortunately, this PR is blocked by #29756.

Roadmap:

• Perform some benchmarks of build time speedups and share the results.
• Test caching crates across different packages.
• Implement rust_bootstrap flag into xbps-src, see xbps-src: add sccache support #30702 (comment)
• Test parallel builds in different masterdirs, see xbps-src: add sccache support #30702 (comment)

[Piraty]

interesting. i looked into icecc for xbps-src myself, scache could be a viable alternative.

[Johnnynator]

This will blow up once you run parallel builds in different masterdirs. sccache always listens on some tcp port on localhost. You would need to figure out how to either allocate a TCP port per masterdir or implement the communication via unix sockets and upstream it.

[Logarithmus]

This will blow up once you run parallel builds in different masterdirs. sccache always listens on some tcp port on localhost. You would need to figure out how to either allocate a TCP port per masterdir or implement the communication via unix sockets and upstream it.

I should definitely test this scenario. I still think this PR can be merged in its current state, because $XBPS_SCCACHE is turned off by default. Maybe I should add a disclaimer in README.md about parallel builds in differrent masterdirs though.

[ericonr]

• how faster do builds get?
• does it work for cooperation between different packages using the same crate?
• I'm against the need to install the package manually, it should be automated in some way (I suggested a solution above)

And it can't be merged if it's waiting on another PR.

[Logarithmus]

• how faster do builds get?
• does it work for cooperation between different packages using the same crate?
• I'm against the need to install the package manually, it should be automated in some way (I suggested a solution above)

And it can't be merged if it's waiting on another PR.

• I'll perform some benchmarks and share the results.
• I think it caches crates across different packages, but more testing is needed to proof that.
• OK, I'll try adding rust_bootstrap into xbps-src, just like you've suggested in xbps-src: add sccache support #30702 (comment)

[github-actions]

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