See http://lists.llvm.org/pipermail/llvm-dev/2019-October/136091.html

arm64e is a specific ABI for pointer authentication in C, C++, 
Objective-C, and Swift.  It is used on iOS 12+ on systems that provide 
ARMv8.3, as well as several other Apple OSes.  This ABI is not yet 
considered “stable” for third-party use because some of the details 
are still evolving

This will likely be necessary in order to work with versions of Xcode (etc) that enable the pointer-authentication features for newer (A12+) chips.

Note that ARMv8.3a support is somewhat orthogonal to this; arm64e presumes/requires ARM8.3a to be available, but the reverse it not necessarily the case, AFAIK.