Deduplicate elapsed time formatting

While it's nice to see my code spreading,
I still prefer to have it at one place.

Change-Id: I7bdb13c47ed7e96227deeb14b0a8070aa40148de
Reviewed-by: Orgad Shaneh <orgads@gmail.com>

src/libs/utils/stringutils.h

@@ -100,6 +100,6 @@ T makeUniquelyNumbered(const T &preferred, const Container &reserved)
     return tryName;
 }
 
-
+QTCREATOR_UTILS_EXPORT QString formatElapsedTime(qint64 elapsed);
 
 } // namespace Utils