fix duplication of file dependency artifacts

Multiple occurrences of the same header file when scanning a cpp file
led to the creation of multiple file dependency artifacts with the
same file path.
The problem was that we did not update the file path in the
ResolvedDependencyCacheItem object.

Change-Id: Id941fe501dc92c998b217ca215ddb92c0c1e1b13
Reviewed-by: Christian Kandeler <christian.kandeler@digia.com>
fix tracking of addition/removal of Q_OBJECT headers

Autotest: TestBlackbox::missingQObjectHeader

Change-Id: I96127c47dfd3a2e38801dc1305ce7f9c528a94e3
Reviewed-by: Christian Kandeler <christian.kandeler@digia.com>
fix cpp property references in DarwinGCC.qbs

Change-Id: Iee2701a0d47def9ccc497d65f665655500d9ccf7
Reviewed-by: Christian Kandeler <christian.kandeler@digia.com>