While merging #1722, #1944, #1947 (different aspects of NDK 19 support), I expect there may be some rough edges to smooth out. This issue exists to track things that need checking.

This is a release blocker, these things need checking before the next release.

• Merge all of Initial migration to NDK r19 (Part I - The core) #1722, [LIBS - PART I] Initial refactor of library recipes #1944, [LIBS - PART II] Part II of NDK r19 migration - Initial STL lib migration #1947 (with appropriate checks along the way).
• Check and fix buildozer's download and use of the correct NDK version (Add ability to get p4a's recommended android's NDK version buildozer#947).
  • Code improvements around NDK download buildozer#961
  • Do a new buildozer release (must be done before the p4a changes hit master)
• Check the min/max supported NDK version
  • consider, do we really need a max?
  • improve the log messages when the NDK version is too low, add details about what p4a version to downgrade to for older version support
• Check as many recipe builds as possible