Temporary fix broken build.ninja after r253790.

FIXME: This can be reverted several hours later.

r253790 introduced cyclic deps around llvm-tblgen and it was affecting after reverting.

  ninja: error: dependency cycle: include/llvm/IR/Attributes.inc -> include/llvm/IR/Attributes.inc.tmp -> bin/llvm-tblgen -> utils/TableGen/CMakeFiles/obj.llvm-tblgen.dir/DFAPacketizerEmitter.cpp.o -> include/llvm/IR/Attributes.inc

It may be a ninja's bug.

FYI, renaming DFAPacketizerEmitter.cpp would be useless.

llvm-svn: 253810