tools::arm::getARMFloatABI() was falling back to guessing soft-float because
it wasn't seeing the GNUEABIHF environment from ComputeEffectivClangTriple
when it was called from gnutools::Assemble::ConstructJob.
Fix by using the effective clang triple in gnutools::Assemble, which now
matches the -triple flag used by cc1 and ClangAs jobs.
Should this just set Triple = llvm::Triple(getToolChain().ComputeEffectiveClangTriple(Args)); here?
In case other stuff in this case statement depends on the triple later.