libcm256cc does not expose its package version through its headers or
shared library, making it impossible to verify a minimum supported
version after discovery leading to errors when building.
When CM256CC_DIR is not specified, use pkg-config to verify that
libcm256cc >= 1.1.2 is available before searching for the headers and
library. If the required version is not found, disable CM256 support
and continue configuring the rest of the project.
When CM256CC_DIR is provided, treat it as an explicit user override and
search that installation directly and blindly (don't check version).
Also update the pkg-config hint variables to use the documented
*_INCLUDE_DIRS and *_LIBRARY_DIRS outputs from pkg_check_modules().
https://cmake.org/cmake/help/latest/module/FindPkgConfig.html
Signed-off-by: Robin Getz <rgetz503@gmail.com>
Robin Getz
0f905d015a