When clang is called as 'target-clang', put deduced target option at
the start of argument list so that option '--target=' specified in command
line could override it.
This change fixes PR34671.
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@313760 91177308-0d34-0410-b5e6-96231b3b80d8
Serge Pavlov