* Android standalone toolchains are not longer necessary
The latest NDK (19) contains ABI/API level specific command line
tools making standalone toolchains unnecessary. This change adapts
to the new model which greatly simplifies the build script and
ensures the latest version of the tools is being used.
Note that this requires a fairly recent version of CMake which fixes
a bug related to ranlib. This change was tested with CMake 3.13
(CMake 3.7 does not work).
* Modify CI build script to fetch recent CMake
* Remove dependency on standalone toolchains in Windows README
* Use correct CMake path
* Update NDK to latest
* Only download CMake and NDK for Android builds
* Add version constant for ninja
* Make output more quiet
