cmd/fpkg/install: deduplicate nix store

Signed-off-by: Ophestra <cat@gensokyo.uk>

cmd/fpkg/install.go

@@ -163,6 +163,8 @@ func actionInstall(args []string) {
 		"rm -rf .local/state/{nix,home-manager}",
 		// run activation script
 		bundle.ActivationPackage + "/activate",
+		// deduplicate nix store
+		"nix store optimise",
 	}, false, func(config *fst.Config) *fst.Config { return config }, bundle, pathSet, dropShellActivate, cleanup)
 
 	/*