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: treehugger
Bug: http://b/146465110
Bug: http://b/147470750
Change-Id: I0b173b7ed5674b270721bc6ec90d546d26ecb968
1 file changed
tree: bcf3c9ae6ea7569e1c2c6ebed9d8de4c8f93470e
  1. r21/
  2. Android.bp
  3. Android.mk
  4. CleanSpec.mk
  5. NOTICE
  6. pylintrc
  7. update.py