CI: replace actions-rs w/ dtolnay/rust-toolchain.

This commit replaces the `actions-rs/toolchain` action with
`dtolnay/rust-toolchain`. The former is no longer maintained.

Usages of `actions-rs/cargo` are replaced with direct invocation of the
relevant tooling installed by `dtolnay/rust-toolchain`.

Author: cpu

.github/workflows/build.yml

@@ -32,10 +32,9 @@ jobs:
           persist-credentials: false
 
       - name: Install ${{ matrix.rust }} toolchain
-        uses: actions-rs/toolchain@v1
+        uses: dtolnay/rust-toolchain@master
         with:
           toolchain: ${{ matrix.rust }}
-          override: true
 
       - name: cargo check (default features)
         run: cargo check --all-targets
@@ -79,11 +78,7 @@ jobs:
           persist-credentials: false
 
       - name: Install rust toolchain
-        uses: actions-rs/toolchain@v1
-        with:
-          toolchain: nightly
-          override: true
-          default: true
+        uses: dtolnay/rust-toolchain@nightly
 
       - name: cargo doc (all features)
         run: cargo doc --all-features --no-deps
@@ -99,17 +94,11 @@ jobs:
         with:
           persist-credentials: false
       - name: Install rust toolchain
-        uses: actions-rs/toolchain@v1
+        uses: dtolnay/rust-toolchain@stable
         with:
-          toolchain: stable
-          override: true
-          default: true
           components: rustfmt
       - name: Check formatting
-        uses: actions-rs/cargo@v1
-        with:
-          command: fmt
-          args: --all -- --check
+        run: cargo fmt --all -- --check
 
   clippy:
     name: Clippy
@@ -120,13 +109,7 @@ jobs:
         with:
           persist-credentials: false
       - name: Install rust toolchain
-        uses: actions-rs/toolchain@v1
+        uses: dtolnay/rust-toolchain@stable
         with:
-          toolchain: stable
-          override: true
-          default: true
           components: clippy
-      - uses: actions-rs/cargo@v1
-        with:
-          command: clippy
-          args: --all-features -- -D warnings
+      - run: cargo clippy --all-features -- --deny warnings