[compiler-rt] [Profile] Disable continuous mode when reset to default.profraw due to malformed LLVM_PROFILE_FILE. (PR #74879)

[Zequan Wu via llvm-commits]

ZequanWu wrote:

> what about printing an error and immediately aborting when LLVM_PROFILE_FILE is invalid?

I think this is better than silently falls back to default.profraw. 
Or we can simply allow multiple `%c` and enable continuous mode as this shouldn't cause any ambiguity. But multiple `%m` might cause ambiguity because it can have `%1m` and `%2m` at the same time and cause ambiguity.

https://github.com/llvm/llvm-project/pull/74879