Update ffmac and HMS

Externalize the hms shell script for easier editing
Update ffmac to latest release
Add copying of Mac apps to the expected folder

overlays/hms.nix

@@ -1,30 +1,3 @@
 { pkgs, ... }:
 
-pkgs.writeShellScriptBin "hms" ''
-set -eo pipefail
-# Build different targets with GUI or not
-
-arch="$(uname -m)"
-if [ "$(uname -s)" == "Darwin" ]; then
-	# On macOS
-	src="$HOME/.config/nix/"
-	target="''${arch}-darwin"
-else
-	# On Linux/WSL2 systems
-	if [ -z "$DISPLAY" ]; then
-		target="''${arch}-nogui"
-	else
-		target="''${arch}-gui"
-	fi
-	src=/etc/nixos
-fi
-
-# Build and switch
-echo "Building $target"
-dest=$(mktemp -d)
-pushd "$dest" > /dev/null
-nix build --impure "$src#homeConfigurations.$target.activationPackage"
-./result/activate
-popd > /dev/null
-rm -r "$dest"
-''
+pkgs.writeShellScriptBin "hms" (builtins.readFile ./hms.sh)