Newer NDKs have RISC-V as experimental ABI (not enabled by default, see
next commit). If we don't have a mapping for a specific target, OpenSSL
falls back to 'android-arm', so that won't really work (interestingly,
it does build).
The build script requires the paths to the NDK and OpenSSL sources.
It runs the build in a Docker container, by default. But if the required
tools are installed on the system (currently jq, make and perl) it can
also be run directly on the system by defining NO_DOCKER.
A relatively recent version of the NDK is required (the pre-built
toolchains are required).
Tobias Brunner