fix rust cache key

Author: 0x7d8

.github/workflows/build.yml

@@ -46,6 +46,7 @@ jobs:
         with:
           toolchain: stable
           target: ${{ matrix.target }}
+          cache-key: ${{ matrix.target }}
 
       - name: Install cross
         run: cargo install cross --git https://github.com/cross-rs/cross