Attempt to fix cuda build and prefix query via pkg-config

Signed-off-by: Dmitry Rogozhkin <[email protected]>

Author: dvrogozh

.github/workflows/linux_cuda_wheel.yaml

@@ -102,6 +102,7 @@ jobs:
           ${CONDA_RUN} nvidia-smi
           ${CONDA_RUN} conda list
           echo LD_LIBRARY_PATH=$CONDA_PREFIX/lib:/usr/local/cuda/lib64/:${LD_LIBRARY_PATH} >> $GITHUB_ENV
+          echo PATH=/usr/local/cuda/bin:${PATH} >> $GITHUB_ENV
       - name: Assert ffmpeg exists
         run: |
           ${CONDA_RUN} ffmpeg -buildconf

test/test_cppapi.py

@@ -59,15 +59,13 @@ def test_cppapi_with_prefix(tmp_path):
     # of its libavcodec.pc file. Potentially, on the custom ffmpeg install with custom layout
     # our calculation can be wrong and test might fail.
     result = subprocess.run(
-        ["pkg-config", "--path", "libavcodec"], capture_output=True, text=True
+        ["pkg-config", "--variable=prefix", "libavcodec"], capture_output=True, text=True
     )
     assert result.returncode == 0
 
     ver = f"{torchcodec.ffmpeg_major_version}"
     my_env = os.environ.copy()
-    my_env[f"TORCHCODEC_FFMPEG{ver}_INSTALL_PREFIX"] = Path(
-        f"{result.stdout}"
-    ).parent.parent.parent
+    my_env[f"TORCHCODEC_FFMPEG{ver}_INSTALL_PREFIX"] = Path(f"{result.stdout.strip()}")
 
     result = subprocess.run(cmake_args, cwd=tmp_path, env=my_env)
     assert result.returncode == 0