cmake @3.31.12 +universal: x86_64 configuration cannot load CLT 27 libxcrun on ARM64

[JeffreyRacine (Jeffrey S. Racine)]

On macOS 27.0 Golden Gate (26A428), ARM64, with MacPorts 2.12.6 and Xcode/CLT 27, building CMake 3.31.12 +universal fails in the Intel configuration path when MacPorts selects Command Line Tools. Rosetta is installed and working.

The Intel-invoked Apple tool shim cannot load:

/Library/Developer/CommandLineTools/usr/lib/libxcrun.dylib

The diagnostic reports:

fat file, but missing compatible architecture (have 'arm64,arm64e', need 'x86_64')

This occurs inside CMake's compiler probe, so the outer error misleadingly reports that /usr/bin/clang cannot compile a simple test program.

A controlled comparison used the same Intel CMake bootstrap:

• With DEVELOPER_DIR selecting CLT, C/C++ configuration failed with the missing x86_64 libxcrun slice.
• With full Xcode selected, whose libxcrun also contains x86_64, C/C++ configuration and builds succeeded. Both ARM64 and Intel test executables were built and run.

A subsequent MacPorts source build of CMake with its saved +universal variant and the command-scoped use_xcode=yes option completed successfully. Both installed CMake architecture slices passed version checks.

The full Xcode selection must reach the build environment; the system's xcode-select setting by itself was insufficient in this case. Please consider requiring/selecting full Xcode for the affected universal build, or another tool invocation that avoids executing a CLT shim under Intel. I have not validated a general repair for other ports or older macOS versions.

The attached toolchain-comparison.txt contains the failed CLT configure log and successful full-Xcode ARM64/x86_64 build logs. Personal scratch paths have been replaced with <scratch>.

[JeffreyRacine (Jeffrey S. Racine)]

Sanitized controlled comparison: CLT libxcrun architecture failure and successful full-Xcode ARM64/x86_64 C/C++ builds using the same Intel CMake bootstrap.