Complete quoting for parameters of some CMake commands

[Markus Elfring]

Some parameters (like "${PROJECT_SOURCE_DIR}/CMakeModules" and "${KICAD_DATA}/scripting/plugins") are passed to CMake commands in your build scripts without enclosing them by quotation marks.
https://github.com/KiCad/kicad-source-mirror/blob/d5e70c93d9be4e138bb26a6f78452466ff6b8cb5/CMakeLists.txt#L16
https://github.com/KiCad/kicad-source-mirror/blob/0dd9efd9db8fc67b8e312cc09b67324838c60246/pcbnew/CMakeLists.txt#L672

I see that these places will result in build difficulties if the contents of the used variables will contain special characters like semicolons.

I would recommend to apply advices from a wiki article.
http://cmake.org/Wiki/CMake/Language_Syntax#CMake_splits_arguments_unless_you_use_quotation_marks_or_escapes.

[Jeff Young (jeyjey)]

I guess if this hasn't bitten us in the last 3 years, and in that same time no one has volunteered to fix it, then it's not going to get fixed.