lang/clover: unbreak with llvm70

llvm/codegen/native.cpp:135:49: error: too few arguments to function call, expected at least 4, have 3

if (tm->addPassesToEmitFile(pm, fos, ft))
    ~~~~~~~~~~~~~~~~~~~~~~~            ^

/usr/local/llvm70/include/llvm/Target/TargetMachine.h:260:3: note: 'addPassesToEmitFile' declared here

virtual bool addPassesToEmitFile(PassManagerBase &, raw_pwrite_stream &,
^

Obtained from: upstream
Approved by: portmgr blanket