Include `llvm-config` and `not` in AppleClang toolchains.

The motivation here is so that we can configure and run compiler-rt
tests from a standalone build against AppleClang.

rdar://75975846

Differential Revision: https://reviews.llvm.org/D100086

GitOrigin-RevId: 73cbc7f60ed90ad207b54b55aaf0efa0e5c38c47
1 file changed