[Nova] Added draft calling GHA workflow for building linux wheels (#2548)

Summary:
As part of Project Nova, we are consolidating CI/CD workflows and infra, making them reusable across PyTorch ecosystem libraries. https://github.com/pytorch/test-infra/pull/460 introduces a general-purpose reusable workflow to build linux wheels for python libraries. This PR introduces a caller workflow that triggers the reusable workflow. Details around modular env setup, passing input args across workflows, etc. are still being worked out.

Using reusable workflow defined in https://github.com/pytorch/test-infra/pull/506

Pull Request resolved: https://github.com/pytorch/audio/pull/2548

Reviewed By: osalpekar

Differential Revision: D38947733

Pulled By: mehtanirav

fbshipit-source-id: 03ab88cef973a092f5c5d1ff8c74ec7ae7e46d01

.github/workflows/build_wheels_linux.yml

+name: Build TorchAudio Linux Wheels
+
+on:
+  workflow_dispatch:
+
+jobs:
+  binary_linux_wheel_py3_8_cu116:
+    uses: pytorch/test-infra/.github/workflows/build_wheels_linux_reusable.yml@main
+    with:
+      repository: "audio"
+      docker_image: "pytorch/manylinux-cuda116"
+      python_version: "3.8"
+      gpu_arch_version: "cu116"

packaging/post_build_script_wheel.sh

+echo "Running post build script..."

packaging/pre_build_script_wheel.sh

+#!/bin/bash
+set -ex
+
+echo "Running pre build script..."
+export FFMPEG_ROOT=${PWD}/third_party/ffmpeg
+if [[ ! -d ${FFMPEG_ROOT} ]]; then
+    packaging/ffmpeg/build.sh
+fi
+echo FFMPEG_ROOT=${FFMPEG_ROOT}