Port "Eclipse CDT settings" file generation from GYP to GN

tools/gn/xml_element_writer.cc

Index: tools/gn/xml_element_writer.cc
diff --git a/tools/gn/xml_element_writer.cc b/tools/gn/xml_element_writer.cc
index 51e0488b53964abd6683cd51e7e5b0b2bf761231..a608ee305eec4ad32dc77903bbc2b9c6efffd818 100644
--- a/tools/gn/xml_element_writer.cc
+++ b/tools/gn/xml_element_writer.cc
@@ -38,7 +38,9 @@ XmlElementWriter::XmlElementWriter(std::ostream& out,
 
 XmlElementWriter::~XmlElementWriter() {
   if (!opening_tag_finished_) {
-    out_ << "/>" << std::endl;
+    // The XML spec does not require a space before the closing slash. However,
+    // Eclipse is unable to parse XML settings files if there is no space.
+    out_ << " />" << std::endl;
   } else {
     if (!one_line_)
       out_ << std::string(indent_, ' ');