Making sure channel flag is set correctly (#2496)

Summary:
Making sure channel flag is set correctly for the test channel

Pull Request resolved: https://github.com/pytorch/audio/pull/2496

Reviewed By: hwangjeff, mthrok

Differential Revision: D37183083

Pulled By: atalman

fbshipit-source-id: 5df8aad1bceb22ad65b0942bf370480bb1cbd44a

.github/workflows/build-m1-binaries.yml

@@ -141,7 +141,7 @@ jobs:
           if [[ $CHANNEL == "test" ]]; then
             setup_cuda
             setup_base_build_version
-            export CONDA_CHANNEL_FLAGS="pytorch-test"
+            export CONDA_CHANNEL_FLAGS="-c pytorch-test"
             setup_macos
           else
             setup_cuda