The `find_package_handle_standard_args(FOUND_VAR)` is deprecated as of
CMake 3.3 and both the `<PackageName>_FOUND` and the upper-cased
`<PACKAGE_NAME>_FOUND` are set with or without using this option.
Additionally, find modules and docs are also synced with this to make it
clearer.
Before calling pkg_check_modules, modules must check PKG_CONFIG_FOUND.
When FindPkgConfig.cmake is loaded, pkg_check_modules is always defined
regardless of pkg-config being present. However, the whole module might
be disabled on user request with CMAKE_DISABLE_FIND_PACKAGE_PkgConfig.
This must not break Find modules which just look for a hint or similar.
Our documented standard for find module variable names is to match the
case of the find module package name. This was overlooked when the
module was added by commit 84e7920b3a (FindFontconfig: Add module to
find Fontconfig, 2018-09-27, v3.14.0-rc1~523^2).
The module was released with the upper case names in CMake 3.14.0, so
fix it to have camel case names in 3.14.1. This is incompatible but
anyone using a given release series should be using the latest patch on
it and we've made breaking fixups on newly released features like this
before.
Reported-by: Christophe Giboudeaux <christophe@krop.fr>
Fixes: #19094
