Special-case paths that appear in libs by not prefixing them with -l.

tools/gn/lib_file.cc

+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "tools/gn/lib_file.h"
+
+#include "base/logging.h"
+
+LibFile::LibFile() {}
+
+LibFile::LibFile(const SourceFile& source_file) : source_file_(source_file) {}
+
+LibFile::LibFile(const base::StringPiece& lib_name)
+    : name_(lib_name.data(), lib_name.size()) {
+  DCHECK(!lib_name.empty());
+}
+
+void LibFile::Swap(LibFile* other) {
+  name_.swap(other->name_);
+  source_file_.swap(other->source_file_);
+}
+
+const std::string& LibFile::value() const {
+  return is_source_file() ? source_file_.value() : name_;
+}
+
+const SourceFile& LibFile::source_file() const {
+  DCHECK(is_source_file());
+  return source_file_;
+}