We still do not compile the Vulkan backend for Android by default, this
simply makes it possible to use the samples on Vulkan with a one-line
change, which is useful for testing purposes.
This change also makes it so that the materials used for the samples
include SPIR-V. This makes them fatter but they are merely samples.
I still consider Vulkan on Android to be experimental, there are some
features that need to be implemented.
* Turn on shaders optimization by default
Release builds of Filament only work well with optimize shaders,
turning optimizations on by default will help avoid mismatches.
This change also adds -g to disable all optimizations, for debug
builds.
* Use -g on debug builds
* Use -g on debug builds
* Update tutorial_redball.md to remove matc's -O
* Update tutorial_suzanne.md to remove matc's -O
* Use -g in debug builds
