[llvm][TextAPI] add simulators to output

Summary:
* for <= tbd_v3, simulator platforms appear the same as the real
platform and we distinct the difference from the architecture.

fixes: rdar://problem/59161559

Reviewers: ributzka, steven_wu

Reviewed By: ributzka

Subscribers: hiraditya, dexonsmith, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D74416