[compiler-rt] minimize_crash.test sometimes one-shots the minimization (fix flaky test) (PR #225544)

[via llvm-commits]

https://github.com/thetruestblue approved this pull request.

lgtm. 
Optional nit: add a comment to explain why it's needed.
`-mutate_depth=2 caps EraseBytes chaining so it can't skip 8->4->2->1 in one shot`

https://github.com/llvm/llvm-project/pull/225544