[libc-commits] [libc] [libc][cmake] disable include tests in overlay mode (PR #114566)

[Nick Desaulniers via libc-commits]

nickdesaulniers wrote:

Ok, I can reproduce at least via `cmake ../runtimes -G Ninja -DLLVM_ENABLE_LLD=ON -DCMAKE_BUILD_TYPE=Debug -DLLVM_ENABLE_RUNTIMES="libc" -DLLVM_LIBC_FULL_BUILD=ON` and `ninja libc_include_tests`.

@michaelrj-google mentioned it might be due to the hunk added by [Sh0g0-1758](https://github.com/Sh0g0-1758) to libc/cmake/modules/LLVMLibCTestRules.cmake in  #111403. But removing that, I can still reproduce the issue.

https://github.com/llvm/llvm-project/pull/114566