[llvm] Support: Do not check if a file exists before executing (PR #128821)

[Matt Arsenault via llvm-commits]

arsenm wrote:

> This seems to be encountering problems on AIX as well: https://lab.llvm.org/buildbot/#/builders/64/builds/2371

Should also be fixed by #129252

https://github.com/llvm/llvm-project/pull/128821