Install cbindgen using a Git commit hash

The hash doubles as a checksum of the code that's downloaded and built. Installing from crates.io doesn't provide equivalent functionality.

.github/workflows/ci.yml

@@ -62,6 +62,7 @@ jobs:
       - uses: actions/checkout@v4
 
       - uses: actions/cache@v4
+        id: cache-cargo
         with:
           path: |
             ~/.cargo/bin/
@@ -72,7 +73,8 @@ jobs:
           key: ${{ runner.os }}-cargo-${{ hashFiles('**/Cargo.lock') }}
 
       - name: Install cbindgen
-        run: cargo install --force cbindgen --version 0.27.0 --locked
+        run: cargo install --locked --git https://github.com/mozilla/cbindgen --rev 58c6156b0d91e82abb03c26187b8d18fa4345ce0 cbindgen
+        if: steps.cache-cargo.outputs.cache-hit != 'true'
 
       - name: Install cargo-llvm-cov
         uses: taiki-e/install-action@cargo-llvm-cov
@@ -111,6 +113,7 @@ jobs:
         shell: bash
         run: |
           cargo build --manifest-path ffi/Cargo.toml
+          cbindgen --version
           cbindgen ffi/ -o ffi/include/loot_condition_interpreter.h
 
       - name: Build and run C++ tests