[clang] [clang] Match -isysroot behaviour with system compiler on Darwin (PR #80524)

[Liviu Ionescu via cfe-commits]

ilg-ul wrote:

> I am suspicious of SDKROOT maybe being in the environment. Can you check if your environment is providing that value under the hood?

I checked and there is no SDKROOT in the environment.


https://github.com/llvm/llvm-project/pull/80524