[compiler-rt] [XRay][RISC-V] Guard trampoline FP saves behind float ABI (PR #214390)

[Mark Zhuang via llvm-commits]

zqb-all wrote:

> > In my opinion, the XRay runtime and the instrumented program should share the same ABI
> 
> This reminds me one thing: currently the backend does require D and C extensions for XRay to work 

Maybe we should change https://github.com/llvm/llvm-project/blob/6b6b913c2a6f2da094f9b35c963c9824d7451384/llvm/lib/Target/RISCV/RISCVSubtarget.h#L312
to 
```cpp
bool isXRaySupported() const override { return  (isSoftFPABI() || hasStdExtD()) && hasStdExtC(); } 
```




https://github.com/llvm/llvm-project/pull/214390