Linux CPU job should respect set Python version (#3477)

Summary:
Reintroduce a conda environment within which we will do all deps installation, audio builds, and tests runs. This conda environment will use the python version set by the GHA job - previously this just defaulted to using the system 3.10 python which was default inside the container.

Pull Request resolved: https://github.com/pytorch/audio/pull/3477

Reviewed By: mthrok

Differential Revision: D47414572

Pulled By: osalpekar

fbshipit-source-id: 80760f82c7726205b29812d576e498db2a7a80a0

.github/scripts/unittest-linux/install.sh

@@ -13,12 +13,17 @@ set -e
 
 case "$(uname -s)" in
     Darwin*)
-        os=MacOSX;;
+        os=MacOSX
+        eval "$($(which conda) shell.bash hook)"
+        ;;
     *)
         os=Linux
         eval "$("/opt/conda/bin/conda" shell.bash hook)"
 esac
 
+conda create -n ci -y python="${PYTHON_VERSION}"
+conda activate ci
+
 # 1. Install PyTorch
 if [ -z "${CUDA_VERSION:-}" ] ; then
     if [ "${os}" == MacOSX ] ; then

.github/scripts/unittest-linux/run_test.sh

@@ -2,7 +2,9 @@
 
 set -e
 
-eval "$(/opt/conda/bin/conda shell.bash hook)"
+eval "$($(which conda) shell.bash hook)"
+
+conda activate ci
 
 python -m torch.utils.collect_env
 env | grep TORCHAUDIO || true