[compiler-rt] [asan] Build the asan_new_delete.cpp C++ slice with -frtti (PR #213077)

[David Justo via llvm-commits]

https://github.com/davidmrdavid approved this pull request.

LGTM. 

For transparency: the new comments in CMakeLists.txt feel a bit verbose when referring to the standard library linkage bit, but I think it's sufficiently fine as-is.

Thanks for the patience here, **let's get this** in so we can proceed. I'll let you merge.

https://github.com/llvm/llvm-project/pull/213077