Revert "Revert rC322769: [RISCV] Propagate -mabi and -march values to GNU assembler."

Summary: Bringing back the code change and simplified test cases to test 32/64 bit targets.

Reviewers: asb, yroux, inouehrs, mgrang

Reviewed By: yroux, inouehrs

Subscribers: cfe-commits, rbar, johnrusso, simoncook, jordy.potman.lists, sabuasal, niosHD

Differential Revision: https://reviews.llvm.org/D42666

llvm-svn: 323894