make test (developer) does not compile with llvm v20.1.3 on OSX

FAILED: my_lib/CMakeFiles/my_lib.dir/Debug/src/my_lib/lib.cpp.o 
/Users/clausklein/.local/bin/cmake -E __run_co_compile --launcher=ccache --tidy="/usr/local/Cellar/llvm/20.1.3/bin/clang-tidy;-extra-arg=-Wno-unknown-warning-option;-warnings-as-errors=*;--extra-arg-before=--driver-mode=g++" --cppcheck="/usr/local/bin/cppcheck;--template=gcc;--enable=style,performance,warning,portability;--inline-suppr;--suppress=internalAstError;--suppress=unmatchedSuppression;--inconclusive;--error-exitcode=2" --source=/Users/clausklein/Workspace/cpp/cpp_vcpkg_project/my_lib/src/my_lib/lib.cpp -- /usr/local/Cellar/llvm/20.1.3/bin/clang++ -Dmy_lib_EXPORTS -DCMAKE_INTDIR=\"Debug\" -I/Users/clausklein/Workspace/cpp/cpp_vcpkg_project/my_lib/include -isystem /Users/clausklein/Workspace/cpp/cpp_vcpkg_project/build/developer/vcpkg_installed/x64-osx/include -g -std=c++23 -fPIC -fcolor-diagnostics --coverage -O0 -g -Wall -Wextra -Wextra-semi -Wshadow -Wnon-virtual-dtor -Wold-style-cast -Wcast-align -Wunused -Woverloaded-virtual -Wpedantic -Wconversion -Wsign-conversion -Wnull-dereference -Wdouble-promotion -Wformat=2 -Wimplicit-fallthrough -Werror -MD -MT my_lib/CMakeFiles/my_lib.dir/Debug/src/my_lib/lib.cpp.o -MF my_lib/CMakeFiles/my_lib.dir/Debug/src/my_lib/lib.cpp.o.d -o my_lib/CMakeFiles/my_lib.dir/Debug/src/my_lib/lib.cpp.o -c /Users/clausklein/Workspace/cpp/cpp_vcpkg_project/my_lib/src/my_lib/lib.cpp
/Users/clausklein/Workspace/cpp/cpp_vcpkg_project/my_lib/src/my_lib/lib.cpp:3:5: error: function 'some_fun' can be made static or moved into an anonymous namespace to enforce internal linkage [misc-use-internal-linkage,-warnings-as-errors]
    3 | int some_fun() {
      |     ^
      | static 
12591 warnings generated.
Suppressed 12590 warnings (12590 in non-user code).
Use -header-filter=.* to display errors from all non-system headers. Use -system-headers to display errors from system headers as well.
1 warning treated as error

Start with my_lib/src/my_lib/lib.cpp, where clang-tidy reports that some_fun needs internal linkage. Run the developer make test configuration to reproduce the failure and verify that compilation succeeds without the warning-as-error failure.