[compiler-rt] Found one more delta to unbreak build for z/os (PR #82789)

[Sean Perry via llvm-commits]

perry-ca wrote:

Thanks for trying this out @rorth.  I agree with you.  The builtins library touches a lot of platform uniqueness and as a result some of these problems can't be avoided.  One thing I have noticed is that you can't run the unit tests for the builtins library unless you have at least one of the other higher level runtime libraries.  That will be a major headache to fix.

The first three look to me like they should be excluded since these aren't being included in builtins.  My quick thought is they need a line like `// REQUIRES: librt_has_XXX`.  I see a couple other tests that define QUAD_PRECISION and have a requires line.

@arichardson any thoughts on the last one?  I'm thinking we tweak the fb_libs.h a little more and use this conditional include structure for this block of code:

```cpp
#elif defined(QUAD_PRECISION)
  #if defined(CRT_HAS_TF_MODE)
    #if defined(CRT_HAS_IEEE_TF)
    #else
      #error Unsupported TF mode type
    #endif
  #elif defined(CRT_LDBL_128BIT)
  #endif
#endif // *_PRECISION
```
I'll put this change up shortly once I try it out.





https://github.com/llvm/llvm-project/pull/82789