[compiler-rt] [profile] Use fprofile-continuous in compiler-rt tests (PR #126617)

[David Tellenbach via llvm-commits]

dtellenbach wrote:

Sorry, I've not been following this really much, does Darwin not relying on counter relocation change anything with respect to using `-fprofile-continuous`? 

Also, I think we should definitely have some tests that are using `%c` since that is a workflow which is established for many years and is expected to be used much more than the explicit flag. I would actually prefer to have both versions tested.

https://github.com/llvm/llvm-project/pull/126617