Fix startup failure: move BUILD_VENV out of job-level env; clean shellcheck

`BUILD_VENV: ${{ runner.temp }}/build_venv` used the `runner` context in a
job-level env: block, where it is not available (only github/inputs/matrix/
needs/secrets/strategy/vars are). actionlint flags this as an error and GitHub
rejects the whole reusable workflow at parse time, so the test_build_wheels_
linux_v2 caller produced 0 jobs and failed immediately ("workflow not running").

Set BUILD_VENV from $RUNNER_TEMP in an early step (via $GITHUB_ENV) instead.

Also clear the remaining actionlint/shellcheck findings on the new v2 file so
the Lint check (which lints the diff, i.e. every line of a new file) passes:
- SC1090: add `# shellcheck disable=SC1090` before each `source "$BUILD_ENV_FILE"`
- SC2155: add `# shellcheck disable=SC2155` on `export PYTORCH_VERSION=$(...)`
- SC2086: quote "$pkg" / "$abs_pkg" in the manylinux repair loop
- SC2115: `rm -rf "${RUNNER_TEMP:?}/"*` (also fixes a quoted-glob bug that
  removed a literal `*` and cleaned nothing)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: atalman

.github/workflows/build_wheels_linux_v2.yml

@@ -179,8 +179,6 @@ jobs:
       UPLOAD_TO_BASE_BUCKET: ${{ matrix.upload_to_base_bucket }}
       ARCH: ${{ inputs.architecture }}
       BUILD_TARGET: ${{ inputs.build-target }}
-      # Where the uv-managed build venv lives; activated in every build/test step.
-      BUILD_VENV: ${{ runner.temp }}/build_venv
     name: build-${{ matrix.build_name }}
     runs-on: ${{ (inputs.runner != '' && inputs.runner) || matrix.validation_runner }}
     environment: ${{(inputs.trigger-event == 'schedule' || (inputs.trigger-event == 'push' && (startsWith(github.event.ref, 'refs/heads/nightly') || startsWith(github.event.ref, 'refs/tags/v')))) && 'pytorchbot-env' || ''}}
@@ -198,10 +196,17 @@ jobs:
           mkdir -p "${GITHUB_WORKSPACE}"
 
           if [[ "${{ inputs.architecture }}" = "aarch64" ]]; then
-            rm -rf "${RUNNER_TEMP}/*"
+            rm -rf "${RUNNER_TEMP:?}/"*
           fi
           echo "::endgroup::"
 
+      # Where the uv-managed build venv lives; activated in every build/test
+      # step. Set here (not in job-level env:) because it needs $RUNNER_TEMP --
+      # the `runner` context is not available in a job-level env: block.
+      - name: Set build venv path
+        shell: bash
+        run: echo "BUILD_VENV=${RUNNER_TEMP}/build_venv" >> "${GITHUB_ENV}"
+
       - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
         with:
           # Support the use case where we need to checkout someone's fork
@@ -333,8 +338,10 @@ jobs:
         shell: bash -l {0}
         run: |
           set -euxo pipefail
+          # shellcheck disable=SC1090
           source "${BUILD_ENV_FILE}"
           export PATH="${BUILD_VENV}/bin:${PATH}"
+          # shellcheck disable=SC2155
           export PYTORCH_VERSION="$(${CONDA_RUN} pip show torch | grep ^Version: | sed 's/Version: *//' | sed 's/+.\+//')"
           echo "Successfully installed Python build package"
           ${CONDA_RUN} ${{ inputs.build-command }}
@@ -345,8 +352,10 @@ jobs:
         shell: bash -l {0}
         run: |
           set -euxo pipefail
+          # shellcheck disable=SC1090
           source "${BUILD_ENV_FILE}"
           export PATH="${BUILD_VENV}/bin:${PATH}"
+          # shellcheck disable=SC2155
           export PYTORCH_VERSION="$(${CONDA_RUN} pip show torch | grep ^Version: | sed 's/Version: *//' | sed 's/+.\+//')"
           ${CONDA_RUN} python setup.py clean
           echo "Successfully ran python setup.py clean"
@@ -359,15 +368,16 @@ jobs:
           SMOKE_TEST_SCRIPT: ${{ inputs.smoke-test-script }}
         run: |
           set -euxo pipefail
+          # shellcheck disable=SC1090
           source "${BUILD_ENV_FILE}"
           export PATH="${BUILD_VENV}/bin:${PATH}"
           for pkg in ${{ inputs.repository }}/dist/*-linux_*.whl; do
             # if the glob didn't match anything
             if [[ ! -e $pkg ]]; then
                 continue
             fi
-            abs_pkg=$(realpath $pkg)
-            ./test-infra/.github/scripts/repair_manylinux_2_28.sh $abs_pkg
+            abs_pkg=$(realpath "$pkg")
+            ./test-infra/.github/scripts/repair_manylinux_2_28.sh "$abs_pkg"
           done
 
       - name: Run Post-Script
@@ -385,6 +395,7 @@ jobs:
           SMOKE_TEST_SCRIPT: ${{ inputs.smoke-test-script }}
         run: |
           set -euxo pipefail
+          # shellcheck disable=SC1090
           source "${BUILD_ENV_FILE}"
           export PATH="${BUILD_VENV}/bin:${PATH}"
           WHEEL_NAME=$(ls "${{ inputs.repository }}/dist/")