[Qbs] Qbs Rule for a tool like syncqt.pl

[Christian Gudrian]

Am 22.01.2019 um 09:34 schrieb Christian Kandeler:
>   and contains/pulls in the Rule that creates the "real" headers

Usually the list of outputArtifacts is known beforehand or can be 
derived from the inputs. What about scenarios where this is not the 
case? Is it "allowed" to perform the actual transformation while 
evaluating the outputArtifacts property, while the prepare step just 
returns dummy command?

Christian