Build fix
This merge request contains a set of changes to improve the build process, especially on MSYS2/MINGW builds and windows cross-builds. It also addresses some inconsistencies in the meson.build files.
Changes include:
- Reformat options file and add configuration summary message.
- Improved doc build: docs now build on MSYS2/MINGW; new auto choice for docs which corresponds to true on native builds and false on cross-builds. xml-insert shell script replaced with python for portability.
- reverse order of SIMD checks so we are not looking for features if they have been disabled.
- Improve portability of git-version check
- Iproved introspection build: add auto option corresponding to true for native builds and false for cross-builds.
- Fix link failure for clang on windows
- Only check for --no-undefined once
- Clean up version script generation - ensure that the dependencies are correctly propgated.
- Add dependency checks for gobject-introspection and vapigen.
- Various small code tweaks.