[CMake] CTest: use 'make -k' instead of 'make -i'

[Marcel Loose]

Hi all,

I noticed that 'ctest -DExperimentalBuild' returns with an exit status
0, even if compiler errors occur. I think that is caused by the fact
that 'make -i' is used. The "-i|--ignore-errors" option causes make to
always exit with status 0. 

Wouldn't it make more sense to use 'make -k' instead? 
The "-k|--keep-going" option tries to build as much as possible, but
won't try to build targets that depend on sources that failed to
compile. Furthermore, and more importantly, 'make -k' will return with
an exit status unequal to 0, if compiler errors occurred. 

Best regards,
Marcel Loose.