[compiler-rt] [rtsan] Make sure rtsan gets initialized on mac (PR #100188)

[Chris Apple via llvm-commits]

cjappl wrote:

Thanks for the merge @vitalybuka !

I went ahead and requested commit access to LLVM, so I'll be able to merge things next time I get approvals. I hope that leads to less clerical tasks on your plate.

https://github.com/llvm/llvm-project/pull/100188