[LLD] Do not print additional newlines after reaching error limit

Summary:
This could previously happen if errors that are emitted after reaching the
error limit. In that case, the flag inside the newline() function will be
set to true which causes the next call to print a newline even though the
actual message will be discarded.

Reviewers: ruiu, grimar, MaskRay, espindola

Reviewed By: ruiu

Subscribers: emaste, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D65198

llvm-svn: 366944