UnitTests: Make fake function inline

Change-Id: I8e0927a80d0bdcde7bd0e91c749d015636d07388
Reviewed-by: Nikolai Kosjar <nikolai.kosjar@qt.io>

tests/unit/mockup/coreplugin/icore.h

@@ -2,7 +2,7 @@
 
 namespace Core {
 namespace ICore {
-static QString userResourcePath()
+inline static QString userResourcePath()
 {
      return QDir::tempPath();
 }