Add Nix flake support with NixOS and Home Manager modules #1381

Job	Run time
macos-Debug	3m 35s
macos-RelWithDebInfo	5m 13s
linux-MinSizeRel	4m 49s
linux-Debug	5m 44s
linux-RelWithDebInfo	7m 18s
msys2-mingw64 (MinSizeRel, false)	5m 1s
msys2-mingw64 (RelWithDebInfo, false)	7m 52s
msys2-mingw64 (Debug, false)	8m 18s
msys2-mingw64 (RelWithDebInfo, true)	6m 50s
	54m 40s

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