cmake uses incorrect linker

[rokas-kbit]

When i try to configure my project i get this error:

[driver] Switching to configure preset: osx
[driver] Switching to build preset: osx-dbg
[driver] Switching to test preset: __defaultTestPreset__
[driver] Switching to package preset: __defaultPackagePreset__
[driver] Switching to workflow preset: __defaultWorkflowPreset__
[main] Configuring project: MyProject 
[proc] Executing command: /home/rokas/dev/osxcross_toolchain/bin/x86_64-apple-darwin23.4-cmake -DCMAKE_INSTALL_PREFIX:STRING=/home/rokas/dev/MyProject/3rdParty/cmake-build/osx/install -DCMAKE_EXPORT_COMPILE_COMMANDS:BOOL=TRUE --no-warn-unused-cli -S/home/rokas/dev/MyProject -B/home/rokas/dev/MyProject/3rdParty/cmake-build/osx -G "Ninja Multi-Config"
[cmake] Not searching for unused variables given on the command line.
[cmake] -- Found OSXCROSS_HOST: x86_64-apple-darwin23.4
[cmake] -- Found OSXCROSS_TARGET_DIR: /home/rokas/dev/osxcross_toolchain/bin/..
[cmake] -- Found OSXCROSS_TARGET: darwin23.4
[cmake] -- Found OSXCROSS_SDK: /home/rokas/dev/osxcross_toolchain/bin/../SDK/MacOSX14.4.sdk
[cmake] -- The C compiler identification is Clang 18.1.3
[cmake] -- The CXX compiler identification is Clang 18.1.3
[cmake] -- Detecting C compiler ABI info
[cmake] -- Detecting C compiler ABI info - failed
[cmake] -- Check for working C compiler: /home/rokas/dev/osxcross_toolchain/bin/x86_64-apple-darwin23.4-clang
[cmake] -- Check for working C compiler: /home/rokas/dev/osxcross_toolchain/bin/x86_64-apple-darwin23.4-clang - broken
[cmake] CMake Error at /home/rokas/dev/deps-prefix/cmake/share/cmake-3.31/Modules/CMakeTestCCompiler.cmake:67 (message):
[cmake]   The C compiler
[cmake] 
[cmake]     "/home/rokas/dev/osxcross_toolchain/bin/x86_64-apple-darwin23.4-clang"
[cmake] 
[cmake]   is not able to compile a simple test program.
[cmake] 
[cmake]   It fails with the following output:
[cmake] 
[cmake]     Change Dir: '/home/rokas/dev/MyProject/3rdParty/cmake-build/osx/CMakeFiles/CMakeScratch/TryCompile-ibk01L'
[cmake]     
[cmake]     Run Build Command(s): /usr/bin/ninja -v cmTC_d1a8e
[cmake]     [1/2] /home/rokas/dev/osxcross_toolchain/bin/x86_64-apple-darwin23.4-clang -DCMAKE_INTDIR=\"Debug\"  -g -MD -MT CMakeFiles/cmTC_d1a8e.dir/Debug/testCCompiler.c.o -MF CMakeFiles/cmTC_d1a8e.dir/Debug/testCCompiler.c.o.d -o CMakeFiles/cmTC_d1a8e.dir/Debug/testCCompiler.c.o -c /home/rokas/dev/MyProject/3rdParty/cmake-build/osx/CMakeFiles/CMakeScratch/TryCompile-ibk01L/testCCompiler.c
[cmake]     [2/2] : && /home/rokas/dev/osxcross_toolchain/bin/x86_64-apple-darwin23.4-clang -g -Wl,-headerpad_max_install_names  CMakeFiles/cmTC_d1a8e.dir/Debug/testCCompiler.c.o -o Debug/cmTC_d1a8e   && :
[cmake]     FAILED: Debug/cmTC_d1a8e 
[cmake]     : && /home/rokas/dev/osxcross_toolchain/bin/x86_64-apple-darwin23.4-clang -g -Wl,-headerpad_max_install_names  CMakeFiles/cmTC_d1a8e.dir/Debug/testCCompiler.c.o -o Debug/cmTC_d1a8e   && :
[cmake]     /usr/bin/ld: unrecognised emulation mode: llvm
[cmake]     Supported emulations: elf_x86_64 elf32_x86_64 elf_i386 elf_iamcu i386pep i386pe
[cmake]     clang: error: linker command failed with exit code 1 (use -v to see invocation)
[cmake]     ninja: build stopped: subcommand failed.
[cmake]     
[cmake]     
[cmake] 
[cmake]   
[cmake] 
[cmake]   CMake will not be able to correctly generate this project.
[cmake] Call Stack (most recent call first):
[cmake]   CMakeLists.txt:2 (project)
[cmake] 
[cmake] 
[cmake] -- Configuring incomplete, errors occurred!
[proc] The command: /home/rokas/dev/osxcross_toolchain/bin/x86_64-apple-darwin23.4-cmake -DCMAKE_INSTALL_PREFIX:STRING=/home/rokas/dev/MyProject/3rdParty/cmake-build/osx/install -DCMAKE_EXPORT_COMPILE_COMMANDS:BOOL=TRUE --no-warn-unused-cli -S/home/rokas/dev/MyProject -B/home/rokas/dev/MyProject/3rdParty/cmake-build/osx -G "Ninja Multi-Config" exited with code: 1

cmake tries to use /usr/bin/ld for some reason. I could solve it by adding this to toolchain.cmake file:

set(CMAKE_LINKER "${OSXCROSS_TARGET_DIR}/bin/${OSXCROSS_HOST}-ld" CACHE FILEPATH "ld")
set(CMAKE_EXE_LINKER_FLAGS "-fuse-ld=${CMAKE_LINKER}")
set(CMAKE_SHARED_LINKER_FLAGS "-fuse-ld=${CMAKE_LINKER}")
set(CMAKE_MODULE_LINKER_FLAGS "-fuse-ld=${CMAKE_LINKER}")

I was surprised that CMAKE_LINKER is not set in the toolchain. Why is that? How is linker supposed to be configured with osxcross?

Edit: this happens on Ubuntu 24.04.