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

[Rainer Orth via llvm-commits]

rorth wrote:

This patch broke the [Solaris/sparcv9 bot](https://lab.llvm.org/buildbot/#/builders/72/builds/263), which unfortunately was completely ignored:
```
XPASS: Builtins-sparc-sunos:: divtc3_test.c
```
Issue #71971 lacks detail to decide if the workaround patch is correct.  I suspect one could simply remove the `XFAIL`, but that might well be just another hack.

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