[clang] Add clang warning if fp exception functions are called without appropriate flags/pragmas (PR #199009)

[Marcos Ramirez Joos via cfe-commits]

maarcosrmz wrote:

@efriedma-quic Created this as the follow-up PR to https://github.com/llvm/llvm-project/pull/187860. The notable changes are:
* Added a check for strict FP support before issuing the warning
* Added a test run for that case (see [fenv-access.c:4](https://github.com/llvm/llvm-project/pull/199009/changes#diff-9a3d067315c2151e2259f05e0465f1ae872eae2d482b0c4b7416c44b0581c81eR4), [fenv-access.c:56-58](https://github.com/llvm/llvm-project/pull/199009/changes#diff-9a3d067315c2151e2259f05e0465f1ae872eae2d482b0c4b7416c44b0581c81eR56-R58))

If there is anything else I should take into account based on the feedback from the original PR, please let me know.

https://github.com/llvm/llvm-project/pull/199009