New Integration test for workspace command-subdir

Build stream was only creating command-subdir for non workspace builds
this has now been fixed, and this regression test should support the
feature.

tests/integration/project/elements/workspace/workspace-commanddir.bst

+kind: manual
+description: Workspace mount test
+
+depends:
+  - filename: base.bst
+    type: build
+
+sources:
+  - kind: local
+    path: files/workspace-mount-src/
+
+variables:
+  command-subdir: build
+
+config:
+  build-commands:
+    - cc -c ../hello.c

tests/integration/workspace.py

@@ -32,6 +32,23 @@ def test_workspace_mount(cli, tmpdir, datafiles):
     assert os.path.exists(os.path.join(cli.directory, 'workspace'))
 
 
+@pytest.mark.integration
+@pytest.mark.datafiles(DATA_DIR)
+def test_workspace_commanddir(cli, tmpdir, datafiles):
+    project = os.path.join(datafiles.dirname, datafiles.basename)
+    workspace = os.path.join(cli.directory, 'workspace')
+    element_name = 'workspace/workspace-commanddir.bst'
+
+    res = cli.run(project=project, args=['workspace', 'open', element_name, workspace])
+    assert res.exit_code == 0
+
+    res = cli.run(project=project, args=['build', element_name])
+    assert res.exit_code == 0
+
+    assert os.path.exists(os.path.join(cli.directory, 'workspace'))
+    assert os.path.exists(os.path.join(cli.directory, 'workspace', 'build'))
+
+
 @pytest.mark.integration
 @pytest.mark.datafiles(DATA_DIR)
 def test_workspace_updated_dependency(cli, tmpdir, datafiles):