Add support for targeting armv6-unknown-cloudabi-eabihf.

I'm in the progress of adding ARMv6 support to CloudABI. On the compiler
side, everything seems to work properly with this tiny change applied.



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@280672 91177308-0d34-0410-b5e6-96231b3b80d8