Implement __isOSVersionAtLeast for Android

Add the implementation of __isOSVersionAtLeast for Android. Currently,
only the major version is checked against the API level of the platform
which is an integer. The API level is retrieved by reading the system
property ro.build.version.sdk (and optionally ro.build.version.codename
to see if the platform is released or not).

Patch by jiyong@google.com

Bug: 150860940
Bug: 134795810
Test: m

Reviewed By: srhines

Differential Revision: https://reviews.llvm.org/D86596