Fix issues with meson build
This MR fixes feedback from @xclaesse and other issues that I found with symlinks and testing on Windows.
- Removes symlinks and replaces them with files to simplify the meson build
- Adds a custom post install script since gnome.post_install assumes the icon-theme.cache is for hicolor. I will upstream an issue to meson for this.
- Reduces the build files to a single meson.build
- Removes all separate win32 build files
Edited by Dan Yeaw