qbs build: Clear file tags of unit test resources.

Otherwise qbs will try to build the cpp files in there.

Change-Id: I8afd776c8e03bd5f2aea5ac254e94168c23290c3
Reviewed-by: Nikolai Kosjar <nikolai.kosjar@theqtcompany.com>

plugins/clangstaticanalyzer/clangstaticanalyzer.qbs

@@ -66,7 +66,13 @@ QtcPlugin {
             "clangstaticanalyzerunittests.cpp",
             "clangstaticanalyzerunittests.h",
             "clangstaticanalyzerunittests.qrc",
-            "unit-tests/**/*",
         ]
     }
+
+    Group {
+        name: "Unit test resources"
+        prefix: "unit-tests/"
+        fileTags: []
+        files: ["**/*"]
+    }
 }