CI: Use cargo install --locked.

This is a workaround for sourcefrog/cargo-mutants#312
and, now that I've thought about it, seems like possibly a good idea in
general.

.github/workflows/ci.yml

@@ -145,8 +145,9 @@ jobs:
     - name: Install tools
       # Note: Swatinem/rust-cache will cache these installed binaries, so we don't have to worry
       # about caching the builds of them.
+      # cargo-mutants is not used in this step but it will be cached for later use.
       run: |
-        cargo install [email protected] [email protected] [email protected]
+        cargo install --locked [email protected] [email protected] [email protected]
 
 
     - run: df -h .
@@ -267,7 +268,7 @@ jobs:
     - name: Install tools
       # These should already be installed but we might have a cache miss, so don't fail in that case.
       run: |
-        cargo install [email protected] [email protected]
+        cargo install --locked [email protected] [email protected]
 
     - run: df -h .
 
@@ -324,7 +325,7 @@ jobs:
 
       # Install cargo-mutants
       # This should usually be already installed, but is present in case of cache miss
-      - run: cargo install --version 24.1.0 cargo-mutants
+      - run: cargo install --locked cargo-mutants@24.1.0
 
       - name: Relative diff
         run: |

.github/workflows/mutants.yml

@@ -22,7 +22,7 @@ jobs:
         run: rustup toolchain install stable --profile=minimal
 
       - name: Install cargo-mutants
-        run: cargo install --version 24.1.0 cargo-mutants
+        run: cargo install --locked cargo-mutants@24.1.0
 
       - name: Run mutation testing for all-is-cubes
         timeout-minutes: 60

.github/workflows/unstable-ci.yml

@@ -99,7 +99,7 @@ jobs:
       # Note: Swatinem/rust-cache will cache these installed binaries, so we don't have to worry
       # about caching the builds of them.
       run: |
-        cargo install [email protected] [email protected]
+        cargo install --locked [email protected] [email protected]
 
     - name: Compile basic tests
       # compile is broken out so we have visibility into compile vs. run times