[compiler-rt] [builtins] Guard the divtc3_test.c test with CRT_HAS_TF_MODE (PR #71876)

[Alexander Richardson via llvm-commits]

https://github.com/arichardson commented:

I am very surprised the librt_has_divtc3 feature is being defined. It sounds like something is going wrong there? Adding the guard looks good to me but we should really figure out why that feature is incorrectly set.

https://github.com/llvm/llvm-project/pull/71876