Try to make it works with module

[ClausKlein]

• BEMAN_USE_MODULES: works
• BEMAN_USE_STD_MODULE maybe?
• find-install-rount-trip-test
• fixed build brew g++-15 on OSX
• fixed build with brew clang-20 with my workarounds OSX no STD MODULE supported from CMake yet!

Note: the module use an empty FILE_SET HEADERS, with this, the installed package can't be used!

see https://discourse.cmake.org/t/why-are-the-build-and-installed-bmi-files-not-used/15367

and https://discourse.bemanproject.org/t/c-20-modules-in-beman-project-libraries/279/39?u=clausklein

"It is not enough to know, you also have to apply. It's not enough to want, you have to do it.”

[ClausKlein]

@ednolan If I install only the module library, you see this error If a user want to use it:

bash-5.3$ CXX=clang++ cmake -S . -B build -D BEMAN_USE_MODULES=1 -D CMAKE_CXX_STANDARD=23 -D BEMAN_USE_STD_MODULE=1 -Wdev --log-level=VERBOSE --fresh
-- CXXFLAGS=-stdlib=libc++
'brew' '--prefix' 'llvm'
-- LLVM_DIR=/usr/local/Cellar/llvm/22.1.0
-- CMAKE_CXX_STDLIB_MODULES_JSON=/usr/local/Cellar/llvm/22.1.0/lib/c++/libc++.modules.json
-- The CXX compiler identification is Clang 22.1.0
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Check for working CXX compiler: /usr/local/Cellar/llvm/22.1.0/bin/clang++ - skipped
-- Detecting CXX compile features
CMake Warning (dev) at /Users/clausklein/.direnv/python-3.14/lib/python3.14/site-packages/cmake/data/share/cmake-4.2/Modules/Compiler/CMakeCommonCompilerMacros.cmake:248 (cmake_language):
  CMake's support for `import std;` in C++23 and newer is experimental.  It
  is meant only for experimentation and feedback to CMake developers.
Call Stack (most recent call first):
  /Users/clausklein/.direnv/python-3.14/lib/python3.14/site-packages/cmake/data/share/cmake-4.2/Modules/CMakeDetermineCompilerSupport.cmake:113 (cmake_create_cxx_import_std)
  /Users/clausklein/.direnv/python-3.14/lib/python3.14/site-packages/cmake/data/share/cmake-4.2/Modules/CMakeTestCXXCompiler.cmake:83 (CMAKE_DETERMINE_COMPILER_SUPPORT)
  CMakeLists.txt:7 (project)
This warning is for project developers.  Use -Wno-dev to suppress it.

-- Detecting CXX compile features - done
-- CMAKE_CXX_IMPLICIT_INCLUDE_DIRECTORIES=/usr/local/Cellar/llvm/22.1.0/include/c++/v1;/usr/local/Cellar/llvm/22.1.0/lib/clang/22/include;/Library/Developer/CommandLineTools/SDKs/MacOSX14.sdk/usr/include
-- CMAKE_CXX_STDLIB_MODULES_JSON=/usr/local/Cellar/llvm/22.1.0/lib/c++/libc++.modules.json
-- BEMAN_USE_MODULES=1
-- BEMAN_USE_STD_MODULE=1
-- CMAKE_CXX_COMPILER_IMPORT_STD=23;26
-- BEMAN_HAS_IMPORT_STD=ON
Examples to be built: transform_view_direct_usage
-- Configuring done (1.1s)
-- Generating done (0.0s)
-- Build files have been written to: /Users/clausklein/Workspace/cpp/beman-project/transform_view/examples/build
bash-5.3$ ninja -C build/
ninja: Entering directory `build/'
[2/12] Scanning /Users/clausklein/.local/lib/cmake/beman.transform_view/modules/transform_view.cppm for CXX dependencies
FAILED: [code=1] CMakeFiles/beman__transform_view_module@synth_50bb36f7aaa7.dir/e891b98e2521.bmi.ddi 
"/usr/local/Cellar/llvm/22.1.0/bin/clang-scan-deps" -format=p1689 -- /usr/local/Cellar/llvm/22.1.0/bin/clang++ -DBEMAN_HAS_IMPORT_STD -DBEMAN_HAS_MODULES -I/usr/local/Cellar/llvm/22.1.0/include -I/usr/local/Cellar/llvm/22.1.0/include/c++/v1 -I/usr/local/Cellar/llvm/22.1.0/lib/clang/22/include -I/Library/Developer/CommandLineTools/SDKs/MacOSX14.sdk/usr/include -isystem /Users/clausklein/.local/include -stdlib=libc++ -std=gnu++26 -stdlib=libc++ --precompile -x c++ /Users/clausklein/.local/lib/cmake/beman.transform_view/modules/transform_view.cppm -c -o CMakeFiles/beman__transform_view_module@synth_50bb36f7aaa7.dir/e891b98e2521.bmi -resource-dir "/usr/local/Cellar/llvm/22.1.0/lib/clang/22" -MT CMakeFiles/beman__transform_view_module@synth_50bb36f7aaa7.dir/e891b98e2521.bmi.ddi -MD -MF CMakeFiles/beman__transform_view_module@synth_50bb36f7aaa7.dir/e891b98e2521.bmi.ddi.d > CMakeFiles/beman__transform_view_module@synth_50bb36f7aaa7.dir/e891b98e2521.bmi.ddi.tmp && mv CMakeFiles/beman__transform_view_module@synth_50bb36f7aaa7.dir/e891b98e2521.bmi.ddi.tmp CMakeFiles/beman__transform_view_module@synth_50bb36f7aaa7.dir/e891b98e2521.bmi.ddi
warning: argument unused during compilation: '-c'
Diagnostics while scanning dependencies for '/Users/clausklein/.local/lib/cmake/beman.transform_view/modules/transform_view.cppm':
warning: argument unused during compilation: '-c'
/Users/clausklein/.local/lib/cmake/beman.transform_view/modules/transform_view.cppm:16:10: fatal error: 'beman/transform_view/transform_view.hpp' file not found
[3/12] Scanning /usr/local/Cellar/llvm/22.1.0/share/libc++/v1/std.cppm for CXX dependencies
ninja: build stopped: subcommand failed.
bash-5.3$```