[VE][compiler-rt] Add VE as a target of crt

SX Aurora VE is an experimental target.  We upstreamed many part of
ported llvm and clang.  In order to continue this move, we need to
support libraries next, then we need to show the ability of llvm for
VE through test cases.  As a first step for that, we need to use
crt in compiler-rt.  VE has it's own crt but they are a part of
proprietary compiler.  So, we want to use crt in compiler-rt as an
alternative.

This patch enables VE as a candidate of crt in compiler-rt.

Reviewed By: phosek, compnerd

Differential Revision: https://reviews.llvm.org/D92748