ci : fix WHISPER_CUDA -> GGML_CUDA

Author: ggerganov

.github/workflows/build.yml

@@ -481,7 +481,7 @@ jobs:
         run: >
           cmake -S . -B ./build -A ${{ matrix.arch }}
           -DCMAKE_BUILD_TYPE=${{ matrix.build }}
-          -DWHISPER_CUDA=${{ matrix.cublas }}
+          -DGGML_CUDA=${{ matrix.cublas }}
           -DWHISPER_SDL2=${{ matrix.sdl2 }}
 
       - name: Build ${{ matrix.cuda-toolkit }}