[LDC] LLD: Avoid parsing -mllvm* command-line options if there aren't any

When invoking the integrated LLD from LDC, it somehow uses a different
global LLVM command-line parser, one with no registered options, so
parsing is guaranteed to fail, even if there are no args.
[It's only needed for LTO codegen options anyway.]

Author: kinke

lld/COFF/Driver.cpp

@@ -1536,7 +1536,7 @@ void LinkerDriver::linkerMain(ArrayRef<const char *> argsArr) {
     v.push_back(arg->getValue());
     config->mllvmOpts.emplace_back(arg->getValue());
   }
-  {
+  if (v.size() > 1) {
     llvm::TimeTraceScope timeScope2("Parse cl::opt");
     cl::ResetAllOptionOccurrences();
     cl::ParseCommandLineOptions(v.size(), v.data());

lld/wasm/Driver.cpp

@@ -1307,8 +1307,10 @@ void LinkerDriver::linkerMain(ArrayRef<const char *> argsArr) {
   v.push_back("wasm-ld (LLVM option parsing)");
   for (auto *arg : args.filtered(OPT_mllvm))
     v.push_back(arg->getValue());
-  cl::ResetAllOptionOccurrences();
-  cl::ParseCommandLineOptions(v.size(), v.data());
+  if (v.size() > 1) {
+    cl::ResetAllOptionOccurrences();
+    cl::ParseCommandLineOptions(v.size(), v.data());
+  }
 
   readConfigs(args);
   setConfigs();