use oxalica/rust-overlay to build conduwuit

overlay/conduwuit/default.nix

@@ -1,9 +1,17 @@
-final: prev: {
+final: prev:
+let
+  newRust = final.rust-bin.fromRustupToolchainFile ./rust-toolchain.toml;
+  newRustPlatform = final.makeRustPlatform {
+    cargo = newRust;
+    rustc = newRust;
+  };
+in
+{
   conduwuit = prev.conduwuit.override (old: {
-    rustPlatform = old.rustPlatform // {
+    rustPlatform = newRustPlatform // {
       buildRustPackage =
         args:
-        old.rustPlatform.buildRustPackage (
+        newRustPlatform.buildRustPackage (
           args
           // {
             version = "0.5.0-rc2";

overlay/conduwuit/rust-toolchain.toml

@@ -0,0 +1,28 @@
+# This is the authoritiative configuration of this project's Rust toolchain.
+#
+# Other files that need upkeep when this changes:
+#
+# * `Cargo.toml`
+# * `flake.nix`
+#
+# Search in those files for `rust-toolchain.toml` to find the relevant places.
+# If you're having trouble making the relevant changes, bug a maintainer.
+
+[toolchain]
+channel = "1.84.0"
+profile = "minimal"
+components = [
+    # For rust-analyzer
+    "rust-src",
+    "rust-analyzer",
+    # For CI and editors
+    "rustfmt",
+    "clippy",
+]
+targets = [
+    #"x86_64-apple-darwin",
+    "x86_64-unknown-linux-gnu",
+    "x86_64-unknown-linux-musl",
+    "aarch64-unknown-linux-musl",
+    #"aarch64-apple-darwin",
+]