Make sure working directory is respected when configured from matrix (#1686)

* Make sure working directory is respected when configured from matrix

* Fix regression by setting Workingdirectory on stepRun instead of step or too early

pkg/runner/testdata/workdir/push.yml

@@ -22,3 +22,13 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - run: '[[ "$(pwd)" == "/tmp" ]]'
+
+  workdir-from-matrix:
+    runs-on: ubuntu-latest
+    strategy:
+      max-parallel: 1
+      matrix:
+        work_dir: ["/tmp", "/root"]
+    steps:
+      - run: '[[ "$(pwd)" == "${{ matrix.work_dir }}" ]]'
+        working-directory: ${{ matrix.work_dir }}