add rust-toolchain.toml

.github/workflows/rust.yml

@@ -22,13 +22,6 @@ jobs:
        sudo apt-get install libzip5 ./mGBA-0.9.0-ubuntu64-focal/libmgba.deb -y && \
        rm -rf mgba.tar.xz mGBA-0.9.0-ubuntu64-focal
     - uses: actions/checkout@v2
-    - name: Nightly rust with required components
-      uses: actions-rs/toolchain@v1
-      with:
-        toolchain: nightly-2021-04-20
-        components: clippy, rust-src
-        override: true
-
     - name: Cache
       uses: actions/cache@v2.1.1
       with:

agb/rust-toolchain.toml

@@ -0,0 +1,3 @@
+[toolchain]
+channel = "nightly"
+components = ["rust-src"]