Create relenv toolchain symlink in GitHub Actions

Python's sysconfig has hardcoded paths expecting toolchains at
~/.local/relenv/toolchain/, but relenv extracts them to
~/.cache/relenv/toolchains/. When pip builds packages with C extensions
like timelib, the build fails with 'gcc command failed: No such file or
directory' because it can't find the compiler at the sysconfig path.

This adds a workflow step to create the symlink after decompressing
dependencies, matching what we do in local container setups.

Fixes functional/integration test failures on Python 3.11+ when tests
create virtualenvs and install requirements that need compilation.

Author: dwoz

.github/workflows/test-action.yml

@@ -221,6 +221,13 @@ jobs:
         run: |
           docker exec ${{ github.run_id}}_salt-test python3 -m nox --force-color -e decompress-dependencies -- linux ${{ matrix.arch }}
 
+      - name: Create relenv toolchain symlink
+        run: |
+          # Python's sysconfig expects toolchain at ~/.local/relenv/toolchain but
+          # relenv extracts to ~/.cache/relenv/toolchains - create symlink
+          docker exec ${{ github.run_id}}_salt-test bash -c \
+            'mkdir -p ~/.local/relenv && ln -sf ~/.cache/relenv/toolchains ~/.local/relenv/toolchain'
+
       - name: Download testrun-changed-files.txt
         if: ${{ fromJSON(inputs.testrun)['type'] != 'full' }}
         uses: actions/download-artifact@v4
@@ -555,6 +562,13 @@ jobs:
         run: |
           docker exec ${{ github.run_id}}_salt-test python3 -m nox --force-color -e decompress-dependencies -- linux ${{ matrix.arch }}
 
+      - name: Create relenv toolchain symlink
+        run: |
+          # Python's sysconfig expects toolchain at ~/.local/relenv/toolchain but
+          # relenv extracts to ~/.cache/relenv/toolchains - create symlink
+          docker exec ${{ github.run_id}}_salt-test bash -c \
+            'mkdir -p ~/.local/relenv && ln -sf ~/.cache/relenv/toolchains ~/.local/relenv/toolchain'
+
       - name: Download testrun-changed-files.txt
         if: ${{ fromJSON(inputs.testrun)['type'] != 'full' }}
         uses: actions/download-artifact@v4