[compiler-rt] [sanitizer] Disable InstallAtForkHandler on Solaris, NetBSD (PR #75659)

[Rainer Orth via llvm-commits]

rorth wrote:

On one hand, that's not surprising given what I reported in [ [asan] Install pthread_atfork #75290 ](https://github.com/llvm/llvm-project/pull/75290) about the `sanitizer_mac.cpp` definition of `FutexWait`.  On the other hand, I'm astonished that this wasn't caught earlier by some bot.

https://github.com/llvm/llvm-project/pull/75659