(1) Sometimes (but not always!) gltfio-android was failing to build due
to two missing ANativeWindow functions. Linking in "android" seems to
fix this, and is consistent with libfilament-jni.
(2) Improve our "build.sh -c" utility by clobbering some additional
Android build directories. This is especially useful after
adding "-Pextra_cmake_args=-DFILAMENT_SUPPORTS_VULKAN=ON", otherwise
Gradle will try to use a cached CMake configuration.
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