Fixes: #28230
The introduction of CMake SHELL prefix in compile options to avoid
symbol de-duplication caused the build flag export feature to fail.
The export itself works, but unfortunately CMake only strips `SHELL`
prefix for its own compiler invocation, and not when exporting the build
flags.
This causes `SHELL` to be present in the Makefile.exports.<language>
files, leading to problems in external build systems.
This is fixed by using `zephyr_get_compile_options_for_lang()` that
strips `SHELL` and use the returned value for the export handling.
To ensure all compile options has been defined, then the inclusion of
`cmake/makefile_exports` has been moved to the end of
`zephyr/CMakeLists.txt` file.
Signed-off-by: Torsten Rasmussen <Torsten.Rasmussen@nordicsemi.no>
a5917f0af4