Upgrade to actions/cache@v2.1.4

Usually, we can follow the rolling major tag (@v2) of actions.
However the recent release (2.1.4) is not yet included. See
https://github.com/actions/cache/issues/528 for more details.

We do want to depend on 2.1.4 because it contains a fix that allows
us to use the cache action MacOS. v2 also features better compression
and allows for multiple paths to be specified.

.github/workflows/ci.yml

@@ -23,7 +23,7 @@ jobs:
           components: rustfmt, clippy
 
       - name: Cache ~/.cargo/bin directory
-        uses: actions/cache@v1
+        uses: actions/cache@v2.1.4
         with:
           path: ~/.cargo/bin
           key: ubuntu-rust-${{ env.RUST_TOOLCHAIN }}-cargo-bin-directory-v1
@@ -67,18 +67,13 @@ jobs:
           profile: minimal
           override: true
 
-      - name: Cache target directory
-        uses: actions/cache@v1
-        if: matrix.os == 'ubuntu-latest'
-        with:
-          path: target
-          key: rust-${{ matrix.target }}-target-directory-build-${{ hashFiles('Cargo.lock') }}-v1
-
-      - name: Cache ~/.cargo/registry directory
-        uses: actions/cache@v1
+      - name: Cache target and registry directory
+        uses: actions/cache@v2.1.4
         with:
-          path: ~/.cargo/registry
-          key: rust-${{ matrix.target }}-cargo-registry-directory-${{ hashFiles('Cargo.lock') }}-v1
+          path: |
+            target
+            ~/.cargo/registry
+          key: rust-${{ matrix.target }}-build-${{ hashFiles('Cargo.lock') }}-v1
 
       - name: Build binary
         run: |
@@ -119,18 +114,13 @@ jobs:
           profile: minimal
           override: true
 
-      - name: Cache target directory
-        uses: actions/cache@v1
-        if: matrix.os == 'ubuntu-latest'
-        with:
-          path: target
-          key: rust-${{ matrix.target }}-target-directory-test-${{ hashFiles('Cargo.lock') }}-v1
-
-      - name: Cache ~/.cargo/registry directory
-        uses: actions/cache@v1
+      - name: Cache target and registry directory
+        uses: actions/cache@v2.1.4
         with:
-          path: ~/.cargo/registry
-          key: rust-${{ matrix.target }}-cargo-registry-directory-${{ hashFiles('Cargo.lock') }}-v1
+          path: |
+            target
+            ~/.cargo/registry
+          key: rust-${{ matrix.target }}-test-${{ hashFiles('Cargo.lock') }}-v1
 
       - name: Build tests
         run: cargo build --tests --workspace --all-features
@@ -166,17 +156,13 @@ jobs:
           profile: minimal
           override: true
 
-      - name: Cache target directory
-        uses: actions/cache@v1
-        with:
-          path: target
-          key: rust-${{ matrix.target }}-target-directory-test-${{ hashFiles('Cargo.lock') }}-v1
-
-      - name: Cache ~/.cargo/registry directory
-        uses: actions/cache@v1
+      - name: Cache target and registry directory
+        uses: actions/cache@v2.1.4
         with:
-          path: ~/.cargo/registry
-          key: rust-${{ env.TARGET }}-cargo-registry-directory-${{ hashFiles('Cargo.lock') }}-v1
+          path: |
+            target
+            ~/.cargo/registry
+          key: rust-${{ matrix.target }}-test-${{ hashFiles('Cargo.lock') }}-v1
 
       - name: Run test ${{ matrix.test_name }}
         run: cargo test --package swap --all-features --test ${{ matrix.test_name }} ""