C++20 modules with cmake 4.3.0 are not cacheable due to `@response` files

[Felixoid]

The line from the integration test #2649 contains @file:

[8/9] /sccache/target/debug/sccache /usr/bin/clang++ -std=c++20 -MD -MT CMakeFiles/myproject.dir/main.cpp.o -MF CMakeFiles/myproject.dir/main.cpp.o.d @CMakeFiles/myproject.dir/main.cpp.o.modmap -o CMakeFiles/myproject.dir/main.cpp.o -c /build/cmake-modules/main.cpp

It causes the compilation result caching failure with

Non-cacheable reasons:
@                                     4

[TroyKomodo]

this is strange, i use cmake 4.1.2 at work and during my initial implementation and had no issues with this, what version of CMake are u using here?

[Felixoid]

The issue is reproduced by the actions

You can checkout
git fetch origin 42afcddcaac67d2c1146fa1b30fea54aa2d4c462 && git checkout 42afcddcaac67d2c1146fa1b30fea54aa2d4c462
and run the docker tests as
make -C tests/integration test-cmake-modules-v4 test-cmake-modules
The full output should be the same as https://github.com/mozilla/sccache/actions/runs/23479900947/job/68320848155?pr=2649#step:3:1425

Here are working and broken versions:

$ docker run integration-test-cmake-modules-v4:latest cmake --version
cmake version 4.3.0
$ docker run integration-test-cmake-modules:latest cmake --version
cmake version 3.31.6