[Driver][RISCV] Add RedHat Linux RISC-V triple

Authored by luismarques on Feb 14 2020, 5:44 AM.


[Driver][RISCV] Add RedHat Linux RISC-V triple

Summary: Adds the RedHat Linux triple to the list of 64-bit RISC-V triples.
Without this the gcc libraries wouldn't be found by clang on a redhat/fedora
system, as the search list included /usr/lib/gcc/riscv64-redhat-linux-gnu
but the correct path didn't include the -gnu suffix.

Reviewers: lenary, asb, dlj
Reviewed By: lenary
Tags: #clang
Differential Revision: https://reviews.llvm.org/D74399