GN: fix a DCHECK() when generating Visual Studio solution files

tools/gn/visual_studio_writer.cc

Index: tools/gn/visual_studio_writer.cc
diff --git a/tools/gn/visual_studio_writer.cc b/tools/gn/visual_studio_writer.cc
index 7748fbe19df46326e53f19630d2b23ee04b7f568..4b64f1eed6a142e7bf4e8ceedf2ded8d463949e3 100644
--- a/tools/gn/visual_studio_writer.cc
+++ b/tools/gn/visual_studio_writer.cc
@@ -606,14 +606,14 @@ void VisualStudioWriter::WriteSolutionFileContents(
   SourceDir solution_dir(FilePathToUTF8(solution_dir_path));
   for (const SolutionEntry* folder : folders_) {
     out << "Project(\"" << kGuidTypeFolder << "\") = \"(" << folder->name
-        << ")\", \"" << RebasePath(folder->path, solution_dir, "/") << "\", \""
+        << ")\", \"" << RebasePath(folder->path, solution_dir) << "\", \""
         << folder->guid << "\"" << std::endl;
     out << "EndProject" << std::endl;
   }
 
   for (const SolutionEntry* project : projects_) {
     out << "Project(\"" << kGuidTypeProject << "\") = \"" << project->name
-        << "\", \"" << RebasePath(project->path, solution_dir, "/") << "\", \""
+        << "\", \"" << RebasePath(project->path, solution_dir) << "\", \""
         << project->guid << "\"" << std::endl;
     out << "EndProject" << std::endl;
   }