chore: update CI, lock files and flake for no_std targets

Author: caarloshenriq

.github/workflows/rust.yml

@@ -145,3 +145,21 @@ jobs:
         uses: Swatinem/rust-cache@v2
       - name: "Build fuzz targets"
         run: cd fuzz && cargo build
+
+  Embedded:
+    name: Embedded build
+    runs-on: ubuntu-latest
+    steps:
+      - name: "Checkout repo"
+        uses: actions/checkout@v4
+      - name: "Install nightly toolchain"
+        uses: dtolnay/rust-toolchain@nightly
+        with:
+          components: rust-src
+          targets: thumbv7em-none-eabihf
+      - name: Install ARM cross compiler
+        run: sudo apt-get update && sudo apt-get install -y gcc-arm-none-eabi
+      - name: "Build embedded target"
+        env:
+          CC_thumbv7em_none_eabihf: arm-none-eabi-gcc
+        run: cargo build -p payjoin --no-default-features --features "alloc,v2" --target thumbv7em-none-eabihf -Zbuild-std=core,alloc

flake.nix

@@ -340,6 +340,24 @@
           AR_wasm32_unknown_unknown = "${pkgs.llvmPackages.bintools-unwrapped}/bin/llvm-ar";
         };
 
+        embeddedRustToolchain = (pkgs.rust-bin.fromRustupToolchainFile ./rust-toolchain.toml).override {
+          extensions = [
+            "rust-src"
+            "rustfmt"
+            "llvm-tools-preview"
+          ];
+          targets = [ "thumbv7em-none-eabihf" ];
+        };
+
+        embeddedDevShell = pkgs.mkShell {
+          name = "embedded-dev";
+          packages = with pkgs; [
+            embeddedRustToolchain
+            gcc-arm-embedded
+          ];
+          CC_thumbv7em_none_eabihf = "arm-none-eabi-gcc";
+        };
+
         dartDevShell = pkgs.mkShell {
           name = "dart-dev";
           packages =
@@ -461,6 +479,7 @@
           javascript = javascriptDevShell;
           csharp = csharpDevShell;
           dart = dartDevShell;
+          embedded = embeddedDevShell;
         };
         formatter = treefmtEval.config.build.wrapper;
         checks =