Update build.yaml

Author: Torwent

.github/workflows/build.yaml

@@ -73,6 +73,12 @@ jobs:
           }
         shell: pwsh
 
+        - name: Verify toolchain
+          run: |
+            where i686-w64-mingw32-gcc
+            where x86_64-w64-mingw32-gcc
+          shell: pwsh
+
       - name: Build for ${{ matrix.target }}
         run: cargo build --release --target=${{ matrix.target }}