Help: minor improvement for the CMAKE_PREFIX_PATH docs
With this patch the CMAKE_PREFIX_PATH env. var. is now mentioned in the help for the CMAKE_PREFIX_PATH cmake var.
I noticed that the environment variable CMAKE_PREFIX_PATH is not mentioned e.g. in the help for find_library(), but simply "CMAKE_PREFIX_PATH" (without clarifying whether it's the cmake or the env. var) is mentioned. Maybe it should ?
Topic-rename: doc-xref-find-env-vars
Edited by Brad King