Install toolchain with rustup directly

Signed-off-by: Joe Richey <joerichey@google.com>

Author: josephlr

.github/workflows/tests.yml

@@ -70,11 +70,10 @@ jobs:
         ]
     steps:
       - uses: actions/checkout@v2
-      - uses: actions-rs/toolchain@v1
-        with:
-          profile: minimal
-          target: ${{ matrix.target }}
-          toolchain: stable
+      - name: Install toolchain/target
+        run: |
+          rustup update stable --no-self-update --profile=minimal --target=${{ matrix.target }}
+          rustup default stable
       - name: Install multilib
         # update is needed to fix the 404 error on install, see:
         # https://github.com/actions/virtual-environments/issues/675
@@ -97,11 +96,10 @@ jobs:
         ]
     steps:
       - uses: actions/checkout@v2
-      - uses: actions-rs/toolchain@v1
-        with:
-          profile: minimal
-          target: ${{ matrix.target }}
-          toolchain: stable
+      - name: Install toolchain/target
+        run: |
+          rustup update stable --no-self-update --profile=minimal --target=${{ matrix.target }}
+          rustup default stable
       - name: Build Tests
         run: cargo test --no-run --target=${{ matrix.target }} --features=std
 
@@ -118,11 +116,9 @@ jobs:
     steps:
       - uses: actions/checkout@v2
       - name: Install toolchain
-        uses: actions-rs/toolchain@v1
-        with:
-          profile: minimal
-          toolchain: ${{ matrix.toolchain }}
-          override: true
+        run: |
+          rustup update ${{ matrix.toolchain }} --no-self-update --profile=minimal
+          rustup default ${{ matrix.toolchain }}
       - run: cargo test --features=std
 
   # TODO: Add emscripten when it's working with Cross