ThinLTO/X86/cache.ll regression test flaky

[thejh]

At the current main branch HEAD (commit 14c95e0c8b25f6deba47cd279c5dcdeef3870159), when running the regression test suite with ninja check-llvm, the ThinLTO/X86/cache.ll regression test sometimes passes for me, but sometimes fails.

When I run the test with bin/llvm-lit test/ThinLTO/X86/cache.ll, it seems to always pass.

I think it failed at different points; but one of the failures was this (failing at the first ; RUN: ls %t.cache.noindex/llvmcache-foo-76 line):

[...]
RUN: at line 123: touch -t 198002051200 [...]/test/ThinLTO/X86/Output/cache.ll.tmp.cache.noindex/llvmcache-foo-76
+ touch -t 198002051200 [...]/test/ThinLTO/X86/Output/cache.ll.tmp.cache.noindex/llvmcache-foo-76
RUN: at line 124: [...]/bin/llvm-lto -thinlto-action=run -exported-symbol=globalfunc [...]/test/ThinLTO/X86/Output/cache.ll.tmp2.bc [...]/test/ThinLTO/X86/Output/cache.ll.tmp.bc -thinlto-cache-dir [...]/test/ThinLTO/X86/Output/cache.ll.tmp.cache.noindex --thinlto-cache-max-size-bytes 78847 --thinlto-cache-entry-expiration 4294967295
+ [...]/bin/llvm-lto -thinlto-action=run -exported-symbol=globalfunc [...]/test/ThinLTO/X86/Output/cache.ll.tmp2.bc [...]/test/ThinLTO/X86/Output/cache.ll.tmp.bc -thinlto-cache-dir [...]/test/ThinLTO/X86/Output/cache.ll.tmp.cache.noindex --thinlto-cache-max-size-bytes 78847 --thinlto-cache-entry-expiration 4294967295
RUN: at line 125: ls [...]/test/ThinLTO/X86/Output/cache.ll.tmp.cache.noindex/llvmcache-foo-8
+ ls [...]/test/ThinLTO/X86/Output/cache.ll.tmp.cache.noindex/llvmcache-foo-8
RUN: at line 126: ls [...]/test/ThinLTO/X86/Output/cache.ll.tmp.cache.noindex/llvmcache-foo-76
+ ls [...]/test/ThinLTO/X86/Output/cache.ll.tmp.cache.noindex/llvmcache-foo-76
ls: cannot access '[...]/test/ThinLTO/X86/Output/cache.ll.tmp.cache.noindex/llvmcache-foo-76': No such file or directory