CI: Lint the crate

We are not currently running the linter in CI, do so.

Lint with three different feature combinations to get reasonable
coverage.

Author: tcharding

.github/workflows/rust.yml

@@ -15,6 +15,8 @@ jobs:
           profile: minimal
           toolchain: nightly
           override: true
+      - name: Install clippy
+        run: rustup component add clippy
       - name: Running benchmarks
         env:
           DO_BENCH: true
@@ -27,6 +29,10 @@ jobs:
         env:
           DO_FMT: true
         run: ./contrib/test.sh
+      - name: Running linter
+        env:
+          DO_LINT: true
+        run: ./contrib/test.sh
 
   Int-tests:
     name: Integration tests

contrib/test.sh

@@ -33,6 +33,14 @@ fi
 # Defaults / sanity checks
 cargo test
 
+if [ "$DO_LINT" = true ]; then
+    clippy="cargo +nightly clippy"
+
+    $clippy --all-features --all-targets -- -D warnings
+    $clippy --all-targets -- -D warnings
+    $clippy --no-default-features --features=no-std --all-targets -- -D warnings
+fi
+
 if [ "$DO_FEATURE_MATRIX" = true ]
 then
     # All features