[Android] On AArch64, Build fails when Running `cross test --target aarch64-linux-android` because it doesn't recognise `__clear_cache` intrinsic.

Tried to use this intrinsic from C (`__builtin__)clear_cache`).  
Tried to use the LLVM export (named `__clear_cache`).  

Both GCC and Clang should recognise this intrinsic, yet build fails (on GCC); but only on ARM based platforms. I have no idea why. Android source itself uses this intrinsic fine. No idea what is going on.