attempt at vulkan CI

Author: russelltg

.github/workflows/build.yml

@@ -53,7 +53,7 @@ jobs:
         ffmpeg_version: ["6.1", "7.0", "7.1", "8.0"]
     env:
       CARGO_PROFILE_DEV_BUILD_OVERRIDE_DEBUG: true
-      FEATURES: avcodec,avdevice,avfilter,avformat,swresample,swscale #,postproc
+      FEATURES: avcodec,avdevice,avfilter,avformat,swresample,swscale,vulkan #,postproc
       FFMPEG_DIR: /home/runner/work/rust-ffmpeg-sys/rust-ffmpeg-sys/ffmpeg-${{ matrix.ffmpeg_version }}-linux-clang-default
     steps:
       - uses: actions/checkout@v2