Add a ``FIND_LIBRARY_USE_LIB32_PATHS`` global property analogous to the
``FIND_LIBRARY_USE_LIB64_PATHS`` property. This helps find commands on
multilib systems that use ``lib32`` directories and either do not have
``lib`` symlinks or point ``lib`` to ``lib64``.
Use CMAKE_PREFIX_PATH, CMAKE_FRAMEWORK_PATH, and CMAKE_APPBUNDLE_PATH
cache and environment variables to extend PKG_CONFIG_PATH before calling
pkg-config.
In each of the path in these variables it searches for lib/pkgconfig.
Then, depending on the system, it searches for
lib/${CMAKE_LIBRARY_ARCHITECTURE}/pkgconfig (debian) or for
lib64/pkgconfig (other 64 bit unixes). If any of these path is found,
it is appended to the PKG_CONFIG_PATH enviromnent variable.
Add two new arguments to the pkg_check_module and pkg_search_module
macro, NO_CMAKE_PATH and NO_CMAKE_ENVIRONMENT_PATH. The new signature
are therefore:
pkg_check_modules(<PREFIX> [REQUIRED] [QUIET]
[NO_CMAKE_PATH] [NO_CMAKE_ENVIRONMENT_PATH]
<MODULE> [<MODULE>]*)
pkg_search_module(<PREFIX> [REQUIRED] [QUIET]
[NO_CMAKE_PATH] [NO_CMAKE_ENVIRONMENT_PATH]
<MODULE> [<MODULE>]*)
By default, if CMAKE_MINIMUM_REQUIRED_VERSION is 3.1 or later (in
order to keep compatibility with the previous behavior), or if
PKG_CONFIG_USE_CMAKE_PREFIX_PATH is set, the CMAKE_PREFIX_PATH,
CMAKE_FRAMEWORK_PATH, and CMAKE_APPBUNDLE_PATH cache and environment
variables will be added to pkgconfig search path.
The NO_CMAKE_PATH and NO_CMAKE_ENVIRONMENT_PATH arguments disable this
behavior for the cache variables and the environment variables,
respectively, similarly to the find_package() command.
