Since commit v2.8.12~327^2 (Qt4Macros: Allow specifying a TARGET
in invokations of macros., 2013-02-26), a parameters file is
populated with moc arguments at generate-time.
When the compile definitions or include directories change, the
parameters file is updated but moc is not re-run in response.
Fix that by making the moc invocation depend on the parameters file.
Reported-At: https://bugreports.qt-project.org/browse/QTBUG-36970
Stephen Kelly