Cmake fails to configure with Xcode generator

[SteveMontgomery]

I checked out the main branch. Cmake fails when configuring for the Xcode generator when clang is included in the project list. The same command with the Ninja generator works fine, i.e.

$ cmake --fresh -G "Xcode" -DCMAKE_BUILD_TYPE=Debug -DLLVM_ENABLE_PROJECTS=clang ../llvm
fails

$ cmake --fresh -G "Xcode" -DCMAKE_BUILD_TYPE=Debug ../llvm
configures OK

$ cmake --fresh -G "Ninja" -DCMAKE_BUILD_TYPE=Debug -DLLVM_ENABLE_PROJECTS=clang ../llvm
configures OK

When configuring for Xcode with clang enabled, there are multiple error messages of the form:
CMake Error at /Users/Steve/Development/llvm-project/clang/cmake/modules/AddClang.cmake:119 (target_compile_definitions):
Cannot specify compile definitions for target "obj.clangBasic" which is not
built by this project.
Call Stack (most recent call first):
/Users/Steve/Development/llvm-project/clang/lib/Basic/CMakeLists.txt:57 (add_clang_library)

I tracked this down to commit 09fa2f0 which certainly seems relevant given it's modified clang/cmake/modules/AddClang.cmake.

[SteveMontgomery]

I should have said that I was using cmake 3.31.2, Xcode 16.2 (16C5032a) on macOS 15.2 (24C101).