Reapply: Hack libc++ support header to work in the platform.

Upstream now supports using ToT libc++ with old NDKs, but as such it
is now *only* compatible with the NDK. That will need to be fixed both
for the platorm and for the NDK-in-platform use case since neither has
android/ndk-version.h.

Original change: https://android-review.googlesource.com/c/platform/prebuilts/ndk/+/827587
I still need up upstream this.

Test: m checkbuild
Bug: None
Change-Id: I90b316c2a193503d25087188f3ada54532eb374c
1 file changed