lib.systems.doubles: add aarch64-windows double

lib/systems/doubles.nix

···
     "wasm64-wasi" "wasm32-wasi"
 
     # Windows
-    "x86_64-windows" "i686-windows"
+    "aarch64-windows" "x86_64-windows" "i686-windows"
   ];
 
   allParsed = map parse.mkSystemFromString all;

lib/tests/systems.nix

···
   testlinux = mseteq linux [ "aarch64-linux" "armv5tel-linux" "armv6l-linux" "armv7a-linux" "armv7l-linux" "i686-linux" "loongarch64-linux" "m68k-linux" "microblaze-linux" "microblazeel-linux" "mips-linux" "mips64-linux" "mips64el-linux" "mipsel-linux" "powerpc64-linux" "powerpc64le-linux" "riscv32-linux" "riscv64-linux" "s390-linux" "s390x-linux" "x86_64-linux" ];
   testnetbsd = mseteq netbsd [ "aarch64-netbsd" "armv6l-netbsd" "armv7a-netbsd" "armv7l-netbsd" "i686-netbsd" "m68k-netbsd" "mipsel-netbsd" "powerpc-netbsd" "riscv32-netbsd" "riscv64-netbsd" "x86_64-netbsd" ];
   testopenbsd = mseteq openbsd [ "i686-openbsd" "x86_64-openbsd" ];
-  testwindows = mseteq windows [ "i686-cygwin" "x86_64-cygwin" "i686-windows" "x86_64-windows" ];
+  testwindows = mseteq windows [ "i686-cygwin" "x86_64-cygwin" "aarch64-windows" "i686-windows" "x86_64-windows" ];
   testunix = mseteq unix (linux ++ darwin ++ freebsd ++ openbsd ++ netbsd ++ illumos ++ cygwin ++ redox);
 })