Improve SSCP std builtins remapping for -ffast-math

[breyerml]

Bug summary
If fast-math is enabled, the JIT compilation (on an NVIDIA GPU) fails when using std::pow inside std::for_each with:

fatal error: error in backend: Undefined external symbol "__powidf2"
[AdaptiveCpp Error] from adaptivecpp/source/include/hipSYCL/glue/llvm-sscp/jit.hpp:265 @ compile(): jit::compile: Encountered errors:
0: LLVMToPtx: clang invocation failed with exit code 70

The same also happens with std::exp:

fatal error: error in backend: Undefined external symbol "exp"
[AdaptiveCpp Error] adaptivecpp/source/include/hipSYCL/glue/llvm-sscp/jit.hpp:265 @ compile(): jit::compile: Encountered errors:
0: LLVMToPtx: clang invocation failed with exit code 70

To Reproduce
Compile a code snippet using C++ standard parallelism on an NVIDIA GPU with AdaptiveCpp v24.02.0

Expected behavior
JIT compilation should not fail.

[illuhad]

We should also look into supporting the functions here: https://gcc.gnu.org/onlinedocs/gccint/Soft-float-library-routines.html which is where the mentioned __powidf2 is listed.

Not sure though why these are specifically emitted with fast-math, seems as this is more related to emulating functions without hardware support.