[Request] Add option for docs

[L4cache]

An option to turn on and off the generation of docs will be nice. I'm implementing a process of building libheif for media-autobuild_suite, I've encountered errors with doxygen, as we are building the command line tool, I think we can disable the docs. But of course fixing the docs generation is also appreciated.

[bradh]

It might be better to split these (since they're essentially unrelated). Also, for the doxygen one, can you show the error(s)?

[L4cache]

FAILED: CMakeFiles/doc_doxygen C:/mabsl/libheif/build/CMakeFiles/doc_doxygen
C:\Windows\system32\cmd.exe /C "cd /D C:\mabsl\libheif\build && C:\mabsl\msys64\usr\bin\doxygen.exe C:/mabsl/libheif/build/Doxyfile"
warning: Tag 'CLANG_ASSISTED_PARSING' at line 1155 of file 'C:/mabsl/libheif/build/Doxyfile' belongs to an option that was not enabled at compile time.
         To avoid this warning please remove this line from your configuration file or upgrade it using "doxygen -u", or recompile doxygen with this feature enabled.
warning: Tag 'CLANG_ADD_INC_PATHS' at line 1161 of file 'C:/mabsl/libheif/build/Doxyfile' belongs to an option that was not enabled at compile time.
         To avoid this warning please remove this line from your configuration file or upgrade it using "doxygen -u", or recompile doxygen with this feature enabled.
warning: Tag 'CLANG_OPTIONS' at line 1169 of file 'C:/mabsl/libheif/build/Doxyfile' belongs to an option that was not enabled at compile time.
         To avoid this warning please remove this line from your configuration file or upgrade it using "doxygen -u", or recompile doxygen with this feature enabled.
warning: Tag 'CLANG_DATABASE_PATH' at line 1182 of file 'C:/mabsl/libheif/build/Doxyfile' belongs to an option that was not enabled at compile time.
         To avoid this warning please remove this line from your configuration file or upgrade it using "doxygen -u", or recompile doxygen with this feature enabled.
error: tag OUTPUT_DIRECTORY: Output directory 'C:/mabsl/libheif/build/apidoc/' does not exist and cannot be created
ninja: build stopped: subcommand failed.

[kmilos]

See also #979

[bradh]

So the warnings are expected and the error looks like an artefact of the build system.

If that cannot be fixed a cmake option could be added.