ci: add mingw arm64 build #471

Job	Run time
Build Debug / flatpak	5m 20s
Build Debug / Nix (x86_64-linux)	17m 52s
Build Debug / build (ubuntu-20.04, 5, linux, 5.12.8, qtnetworkauth)	2m 46s
Build Debug / Nix (x86_64-darwin)	24m 23s
Build Debug / build (ubuntu-20.04, 6, linux, 6.2.4, qt5compat qtimageformats qtnetworkauth)	3m 58s
Build Debug / Nix (aarch64-darwin)	9m 52s
Build Debug / build (windows-2022, Windows-MinGW-w64, clang64, x86_64, amd64_x86)	11m 59s
Build Debug / build (windows-2022, Windows-MinGW-arm64, clangarm64, clang-aarch64, amd64_arm64)	2m 25s
Build Debug / build (windows-2022, Windows-MSVC, x64, amd64, 6, windows, 6.7.3, qt5compat qtimageformats qtnetw...	6m 30s
Build Debug / build (windows-2022, Windows-MSVC-arm64, arm64, amd64_arm64, 6, windows, win64_msvc2019_arm64, 6....	6m 10s
Build Debug / build (macos-14, macOS, 11, 6, mac, 6.7.3, qt5compat qtimageformats qtnetworkauth)	5m 6s
Build Debug / build (macos-14, macOS-Legacy, 10.13, 5, mac, 5.15.2, qtnetworkauth)	3m 34s
	1h 39m 55s

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