ci: change permissions in WS for reusable build

For self-host runners, where the workspace with sources is saving
between different workflow runs, it is needed to be sure that all file
permissions are correct for running user to be sure that later call to
sources checkout action by the same user won't fail on sources cleanup.

Follows up tarantool/tarantool-qa#102

.github/workflows/reusable_build.yml

@@ -27,6 +27,10 @@ jobs:
       OS: ${{ inputs.os }}
       DIST: ${{ inputs.dist }}
     steps:
+      # Permissions correction is needed for self-host runners,
+      # where work path is saved between different workflows runs.
+      - name: 'Correct file permissions in the workspace'
+        run: sudo chown -R $(id -u):$(id -g) .
       - uses: actions/checkout@v2
         with:
           ref: ${{ inputs.ref }}