[CMake] cmake_check_build_system

[Scott Amort]

William A. Hoffman wrote:
> Something like this:
> 
> #########################################################################
> # Disallow in-source build
> STRING(COMPARE EQUAL "${ParaView_SOURCE_DIR}" 
>   "${ParaView_BINARY_DIR}" INSOURCE)
> IF(INSOURCE)
>   MESSAGE(FATAL_ERROR "ParaView requires an out of source Build. Please create a separate binary directory and run CMake there.")
> ENDIF(INSOURCE)

Great!  Thanks Bill.

Scott