Fix ExecuTorch pinned commit update failure (pytorch#117518)

pytorch#117003 shows in interesting failure in which building ExecuTorch runner fails because it needs the change from pytorch#117378.  This reveals a chicken-and-egg bug in the job setup where building ExecuTorch runner depends on PyTorch and thus couldn't be part of the Docker image build where PyTorch is not yet available.  The failure happens because an outdated version of PyTorch is there on the Docker image.

So, like vision and audio, the step to build ExecuTorch runner needs to be done during test time.

I also fix the installation of vision and audio in ET job because they are now installed using PyTorch pinned commits as usual after pytorch/executorch#1247
Pull Request resolved: pytorch#117518
Approved by: https://github.com/larryliu0820, https://github.com/malfet

.ci/docker/ci_commit_pins/executorch.txt

@@ -1 +1 @@
-663882fe7dc518c04adf3d2ee5ccb7d99f41ade4
+2d39c223f23fbd6cc063e06f3374cb107e229a31

.ci/docker/common/install_executorch.sh

@@ -48,7 +48,6 @@ setup_executorch() {
 
   install_flatc_from_source
   pip_install .
-  build_executorch_runner "cmake"
 
   # Make sure that all the newly generate files are owned by Jenkins
   chown -R jenkins .

.ci/pytorch/test.sh

@@ -1034,14 +1034,17 @@ test_docs_test() {
 }
 
 test_executorch() {
+  echo "Install torchvision and torchaudio"
+  install_torchvision
+  install_torchaudio
+
   pushd /executorch
 
-  echo "Install torchvision and torchaudio"
-  # TODO(huydhn): Switch this to the pinned commits on ExecuTorch once they are
-  # there.  These libraries need to be built here, and not part of the Docker
-  # image because they require the target version of torch to be installed first
-  pip_install --no-use-pep517 --user "git+https://github.com/pytorch/audio.git"
-  pip_install --no-use-pep517 --user "git+https://github.com/pytorch/vision.git"
+  # NB: We need to build ExecuTorch runner here and not inside the Docker image
+  # because it depends on PyTorch
+  # shellcheck disable=SC1091
+  source .ci/scripts/utils.sh
+  build_executorch_runner "cmake"
 
   echo "Run ExecuTorch regression tests for some models"
   # NB: This is a sample model, more can be added here