The Android platform does not have ndk-version.h, but it will always
have up-to-date libc headers, so it does not need any compatibility
code intended for past versions of NDK_MAJOR. If ndk-version.h is missing,
assume NDK_MAJOR is (conceptually) infinite
Bug: https://buganizer.corp.google.com/issues/222341313
Test: None
We do ship those headers, so the directory name should not be something
that can potentially conflict with user-defined directories.
Differential Revision: https://reviews.llvm.org/D95956