Generated source code files with qmake

[ludde]

Trying to make qmake work with a project that contains generated source code files.
I want the files to be generated, and then compiled, when I run 'make' and removed when I do 'make clean'.

I found a way to do this, using the somewhat obscure QMAKE_EXTRA_COMPILERS feature.
However, my code generator creates several .cpp files from a single source file, and it seems like QMAKE_EXTRA_COMPILERS only expects a single file to be generated.
I.e., setting .output to a list of files does not work, only the first one gets compiled.

Does anyone have an idea on how to make QMAKE_EXTRA_COMPILERS handle several output files, or maybe an idea on how to accomplish what I want in some other way?