Add TSMUXER_COVERAGE which will result in building binaries with coverage information when set to true.
Move MSVC flag utf-8 from tsMuxerGUI to the general CMakeLists.txt as there is no reason not to enable it globally.
Replace NOT MSVC with checking if the build is for Linux : the effect is the same, but the intent is clearer.
Restructure the platform-specific conditions for building tsMuxerGUI.
Bind the XP build to windows-2019 hosts as windows-2022 includes Visual Studio 2022 which dropped XP support.
Don't install zlib via homebrew in macos in order to avoid conflicts with the system-provided one.
