nix: remove subflake

nix/static.nix

@@ -0,0 +1,27 @@
+{
+  lib,
+  refraction,
+  rust-overlay,
+  pkgsCross,
+}: {arch}: let
+  targets = with pkgsCross; {
+    x86_64 = musl64.pkgsStatic;
+    aarch64 = aarch64-multiplatform.pkgsStatic;
+  };
+
+  getRustcTarget = pkgs: pkgs.stdenv.hostPlatform.rust.rustcTarget;
+  toolchain = rust-overlay.rust.minimal.override {
+    extensions = ["rust-std"];
+    targets = lib.mapAttrsToList (lib.const getRustcTarget) targets;
+  };
+
+  mkRustPlatformWith = pkgs:
+    pkgs.makeRustPlatform (
+      lib.genAttrs ["cargo" "rustc"] (lib.const toolchain)
+    );
+  rustPlatforms = lib.mapAttrs (lib.const mkRustPlatformWith) targets;
+in
+  refraction.override {
+    rustPlatform = rustPlatforms.${arch};
+    optimizeSize = true;
+  }