[Qbs] Use compiler flags file generated by a rule

[Christian Kandeler]

On Thu, 29 Aug 2019 13:19:49 +0200 (CEST)
"Richard Weickelt" <richard at weickelt.de> wrote:

> I want to integrate a generator tool into a Qbs build flow. This tool is very slow and produces a bunch of .h/.c files and a "compiler.opt" file with some compiler flags. I need to use these flags to build the current product and also export them to dependent products.

I don't see how to achieve the seond part, at least not for general options. The first one should be possible by massaging the system a little:
    - Declare the .opt file as the sole output of the rule that runs the generator.
    - Have a second rule that takes the .opt file as an input.
    - Pretend that this rule creates the .h and .cpp files.
    - In the outputArtifacts script, read the .opt file and set cpp.cxxFlags on the outputs accordingly.
    - The actual command is a no-op.

Christian