[libcxx-commits] [libcxx] [libcxxabi] Added support ccache for speedup recompilation libcxx and libcxxabi (PR #78470)

[Vitaly Buka via libcxx-commits]

vitalybuka wrote:

> Caching the tests would provide a huge speedup but as @philnik777 mentioned, it's a really scary thing to do and defeats one of the primary goals we have in the test suite, which is to test-as-we-ship.

1. It does not need to be default ON. 
2. May help with development velocity.
3. some slow bots may benefit, like with sanitizers. When there is some risk from invalid dependency, but more build cycles likely overweight the risk.
4. To be fair, we have just 1 of ~10 bots where we can use ccache in cxx tests. The rest rebuilds compiler from the HEAD, invalidating ccache.



https://github.com/llvm/llvm-project/pull/78470