WIP: Android: Add hooks for NDK to replace CMake Platform/Android* modules
The Android NDK comes with a toolchain file that intends to handle all
Android-related settings and avoid using CMake's own Android support.
However, it includes many settings in the toolchain file itself that are
supposed to belong in
Platform/Android*.cmake modules. Normally
third-party platforms can be configured using a toolchain file that sets
CMAKE_MODULE_PATH to a directory with
but that does not work when CMake comes with builtin modules for that
platform due to policy CMP0017.
Add an undocumented
CMAKE_ANDROID_NDK_HOOK_DIR variable for use by the
Android NDK's toolchain file to specify a directory with modules that
hook into CMake's modules. Teach each
to include a like-named module from the specified hook directory and
then skip the rest of its logic. Also offer a per-module option to not
skip the rest of its logic, just in case.
This hook is needed for any
Platform/Android*.cmake module that is
included by other CMake builtin modules since CMP0017 prevents
CMAKE_MODULE_PATH from overriding such includes.