I've searched and it seems that at some point __NDK_MAJOR__
was at least proposed but at least as of NDK 15c it doesn't seem to be set.
Is there a way within the preprocessor to determine the NDK version being used to build from source?
It's in r16. If you need to know the version before then, you'll need to parse the $NDK/source.properties
file and pass it as a define to your code as part of your build system.