use Cargo.toml & Cargo.lock for sccache build dependency

.github/workflows/build.yml

@@ -104,24 +104,19 @@ jobs:
     name: ${{ matrix.name }}
     steps:
 
-    # sccache's handling of the /fp:fast MSVC compiler option is broken, so use our fork with the fix.
-    # https://github.com/mozilla/sccache/issues/950
     - name: "[Windows] Set up cargo cache"
       if: runner.os == 'Windows'
       uses: actions/cache@v2
       id: sccache-build-cache
       with:
         path: C:\Users\runneradmin\.cargo
-        # hash of commit to build
-        key: e12434e4db24ccbe52b83fb6e37afcb94fc8d37b
+        key: ${{ runner.os }}-cargo-${{ hashFiles('**/Cargo.lock') }}
 
     # This needs to be done first because something later messes with $PATH in a way that breaks cargo
     # by causing it to find link.exe from Git for Windows instead of MSVC.
     - name: "[Windows] Build fixed sccache"
-      shell: bash
       if: runner.os == 'Windows' && steps.sccache-build-cache.outputs.cache-hit != 'true'
-      # TODO: change this to simply `cargo install sccache` after 0.2.16 has been released
-      run: cargo install --git https://github.com/mozilla/sccache.git --branch master
+      run: cargo update
 
     - name: "Check out repository"
       uses: actions/checkout@v2