Add miri testing

Author: palfrey

.github/workflows/ci.yml

@@ -76,4 +76,17 @@ jobs:
           command: bench
         env:
           COUNTS: 0,10,1000,100000,10000000
-        if: ${{ matrix.rust != '1.32.0' }}
+        if: ${{ matrix.rust != '1.32.0' }}
+
+  miri:
+    name: MIRI testing
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2.3.4
+      - uses: actions-rs/toolchain@v1.0.7
+        with:
+          profile: minimal
+          toolchain: nightly
+          override: true
+      - name: Run miri
+        run: ./ci/miri.sh

ci/miri.sh

@@ -9,7 +9,4 @@ rustup component add miri
 
 # Run tests
 cargo miri test
-cargo miri test --target=mips64-unknown-linux-gnuabi64 # big-endian architecture
-
-# Restore old state in case Travis uses this cache for other jobs.
-rustup default nightly
+cargo miri test --target=mips64-unknown-linux-gnuabi64 # big-endian architecture