[CMake] Re: Custom build step

[Brandon Van Every]

I'm going to take a wild guess that one of your variables is emitting
extra quotes or open parentheses or something, such that the 2nd
ADD_CUSTOM_COMMAND gratuitously disappears.  Suggest you message() all
your variables to see what they are, and also write a small test case
that simulates the behavior you're trying to implement, without all
the fancy extra logic.

Cheers,
Brandon Van Every