Changing it to use ninja instead as it builds and runs with ninja.
It looks like you are modifying a step in ClangCMakeBuildFactory to use ninja instead of make. My worry is that this factory is used in a number of bots (see config/builders.py) not only PowerPC bots. It this going to cause problems on other platforms? Other bots?
Sorry for reverting your patches, but I do not see a quick and easy way to fix the problems it has introduced.
Besides, with your last change to use ninja to run tests I don't think you need all these changes after all. It looks like you can use UnifiedTreeBuilder as is and it will do what you want. If not, we can discuss what is missing,
Though, for the sake of completeness of this review, please see my comments inline.
You cannot concatenate a string with WithProperties.
The same is here. No string and WithProperties concatenations.
lnt_setup is not defined if cmake_test_suite is True.