Only override the target architecture on -m32 and friends if it is
actually different. Fixes a surprising link error with nodejs on rpi,
where armv6-netbsd-eabihf turned into armv5e-netbsd-eabihf, which
doesn't lacks the necessary VFP support.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@217546 91177308-0d34-0410-b5e6-96231b3b80d8