CMake provides a user package registry (stored in ~/.cmake/packages) and
a system package registry (not available on non-Windows platforms).
The "export(PACKAGE)" command may store information in the user package
registry, and the "find_package()" command may search both user and
system package registries for information.
This sets various variables to disable the use of these package
registries (both saving and retrieval of package information).
This also sets deprecated variables that perform similar functions, in
case external toolchains include older versions of CMake.
Signed-off-by: Jeffery To <jeffery.to@gmail.com>
