Proper construction of build config

Author: robballantyne

.github/workflows/build-cuda.yml

@@ -144,7 +144,7 @@ jobs:
               echo '=== Configuring build with Ninja ==='
               cmake -B build -S . \
                 -G Ninja \
-                -DCMAKE_EXE_LINKER_FLAGS="-L/usr/local/cuda/lib64/stubs"
+                -DCMAKE_EXE_LINKER_FLAGS="-L/usr/local/cuda/lib64/stubs" \
                 -DGGML_CUDA=ON \
                 -DCMAKE_CUDA_ARCHITECTURES='${{ matrix.architectures }}' \
                 -DCMAKE_BUILD_TYPE=Release \