[clang] Fix bug with -ffp-contract=fast-honor-pragmas (PR #104857)

[Zahira Ammarguellat via cfe-commits]

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

LGTM. Thanks.
I had to double check, but it looks like the LIT test `ffp-contract-fast-honor-pragma-option.cpp` has the same behavior with and without this patch. Right? Aren't there already tests that check the output of the option? 

https://github.com/llvm/llvm-project/pull/104857