ci: Use github action for installing rust

Using `actions-rs/toolchain@v1` could simplify the effort on installing
rust.

Signed-off-by: Gris Ge <cnfourt@gmail.com>

.github/workflows/clippy-rustfmt.yml

@@ -19,11 +19,11 @@ jobs:
       - uses: actions/checkout@v2
 
       - name: Install Rust Nightly
-        run: |
-          rustc -vV
-          rustup toolchain install nightly --allow-downgrade --component=clippy,rustfmt --profile=minimal
-          rustup default nightly
-          rustc -vV
+        uses: actions-rs/toolchain@v1
+        with:
+            toolchain: nightly
+            override: true
+            components: rustfmt, clippy
 
       - name: rustfmt
         run: cargo fmt --all -- --check

.github/workflows/main.yml

@@ -16,11 +16,10 @@ jobs:
       - uses: actions/checkout@v2
 
       - name: Install Rust Stable
-        run: |
-          rustc -vV
-          rustup update stable
-          rustup default stable
-          rustc -vV
+        uses: actions-rs/toolchain@v1
+        with:
+            toolchain: stable
+            override: true
 
       - name: test (netlink-sys)
         run: |