Try using a composite action instead of workflow

.github/actions/setup/action.yml

@@ -0,0 +1,45 @@
+name: Setup
+description: Set up CI environment for Rust + 3DS development
+
+inputs:
+  toolchain:
+    description: The Rust toolchain to use for the steps
+    required: true
+    default: nightly
+
+runs:
+  using: composite
+  steps:
+    # https://github.com/nektos/act/issues/917#issuecomment-1074421318
+    - if: ${{ env.ACT }}
+      shell: bash
+      name: Hack container for local development
+      run: |
+          curl -fsSL https://deb.nodesource.com/setup_lts.x | sudo -E bash -
+          sudo apt-get install -y nodejs
+
+    - name: Checkout branch
+      uses: actions/checkout@v2
+
+    - name: Setup default Rust toolchain
+      # Use this helper action so we get matcher support
+      # https://github.com/actions-rust-lang/setup-rust-toolchain/pull/15
+      uses: actions-rust-lang/setup-rust-toolchain@v1
+      with:
+        components: clippy, rustfmt, rust-src
+        toolchain: ${{ matrix.toolchain }}
+
+    - name: Install build tools for host
+      shell: bash
+      run: sudo apt-get update && sudo apt-get install -y build-essential
+
+    - name: Install cargo-3ds
+      uses: actions-rs/cargo@v1
+      with:
+        command: install
+        # TODO: this should probably just be a released version from crates.io
+        # once cargo-3ds gets published somewhere...
+        # also switch to hash once feature/doctests gets merged
+        args: >-
+          --git https://github.com/rust3ds/cargo-3ds
+          --rev feature/doctests

.github/workflows/ci.yml

@@ -9,6 +9,10 @@ on:
       - master
   workflow_dispatch:
 
+env:
+  # https://blog.rust-lang.org/2022/06/22/sparse-registry-testing.html
+  CARGO_UNSTABLE_SPARSE_REGISTRY: "true"
+
 jobs:
   lint:
     strategy:
@@ -21,8 +25,9 @@ jobs:
     # But if latest nightly fails, allow the workflow to continue
     continue-on-error: ${{ matrix.toolchain == 'nightly' }}
     runs-on: ubuntu-latest
+    container: devkitpro/devkitarm
     steps:
-      - uses: ./.github/workflows/setup.yml
+      - uses: ./.github/actions/setup
         with:
           toolchain: ${{ matrix.toolchain }}
 
@@ -44,8 +49,9 @@ jobs:
           - nightly
     continue-on-error: ${{ matrix.toolchain == 'nightly' }}
     runs-on: ubuntu-latest
+    container: devkitpro/devkitarm
     steps:
-      - uses: ./.github/workflows/setup.yml
+      - uses: ./.github/actions/setup
         with:
           toolchain: ${{ matrix.toolchain }}