Add comments.

llvm-svn: 288111

lld/COFF/DriverUtils.cpp

@@ -666,8 +666,11 @@ llvm::opt::InputArgList ArgParser::parse(ArrayRef<const char *> ArgsArr) {
   return Args;
 }
 
+// link.exe has an interesting feature. If LINK environment exists,
+// its contents are handled as a command line string. So you can pass
+// extra arguments using the environment variable.
 llvm::opt::InputArgList ArgParser::parseLINK(ArrayRef<const char *> Args) {
-  // Concatenate LINK env and given arguments and parse them.
+  // Concatenate LINK env and command line arguments, and then parse them.
   Optional<std::string> Env = Process::GetEnv("LINK");
   if (!Env)
     return parse(Args);