Looks good, but in this repository we're facing https://travis-ci.org/ruby/ruby/jobs/598321906

cp: cannot create regular file '../../.ext/common/pathname.rb': Permission denied
make[2]: *** [../../.ext/common/pathname.rb] Error 1
Makefile:207: recipe for target '../../.ext/common/pathname.rb' failed
make[2]: Leaving directory '/home/travis/build/ruby/ruby/build/ext/pathname'
exts.mk:250: recipe for target 'ext/pathname/all' failed
make[1]: Leaving directory '/home/travis/build/ruby/ruby/build'
make[1]: *** [ext/pathname/all] Error 2
uncommon.mk:293: recipe for target 'build-ext' failed
make: *** [build-ext] Error 2

I suspected it's due to ccache / travis cache issues, but it has failed several times even after purging all Travis cache on ruby/ruby. Maybe we should drop build cache (at least for arm64)?

Looks good, but in this repository we're facing https://travis-ci.org/ruby/ruby/jobs/598321906

I see. I have never seen the error when running on my forked repository.

I suspected it's due to ccache / travis cache issues, but it has failed several times even after purging all Travis cache on ruby/ruby. Maybe we should drop build cache (at least for arm64)?

Sure. I am okay to drop the build cache at least for arm64.
But I have no idea about how to drop it.

OK. We could do that separately. Let's see what happens on master branch first. As it worked on your fork, something might happen at some point.

Thanks for your help!

The #34599.8 (the commit "Disable ccache on arm64 build" on master branch) is failed as we expected.
https://travis-ci.org/ruby/ruby/jobs/598491697#L2574

1)
Process.spawn joins the specified process group if pgroup: pgid FAILED
Expected (STDOUT): "0"
          but got: "33412"
Backtrace
/home/travis/build/ruby/ruby/spec/ruby/core/process/spawn_spec.rb:334:in `block (3 levels) in <top (required)>'
/home/travis/build/ruby/ruby/spec/ruby/core/process/spawn_spec.rb:32:in `<top (required)>'
Finished in 134.152915 seconds
3775 files, 30931 examples, 128704 expectations, 1 failure, 0 errors, 0 tagged

But the next commit, that is #34600.8 (the commit "Remove arm64 build from Drone" on master branch), is failed again for cp: cannot create regular file '../../.ext/common/pathname.rb': Permission denied.
https://travis-ci.org/ruby/ruby/jobs/598491972#L2318

Hmm, right. Maybe we need some another workaround like updating timestamp of files recursively on our own.