Ignore /natvis option for now.

/natvis is a new command line option introduced by MSVC 2017.
We eventually have to support it, but for now, let's ignore it so that
we can at least link stuff instead of printing out an error.

Patch by Michael Rickert.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@312966 91177308-0d34-0410-b5e6-96231b3b80d8

Author: rui314

COFF/Driver.cpp

@@ -241,6 +241,7 @@ void LinkerDriver::parseDirectives(StringRef S) {
     case OPT_editandcontinue:
     case OPT_fastfail:
     case OPT_guardsym:
+    case OPT_natvis:
     case OPT_throwingnew:
       break;
     default:

COFF/Options.td

@@ -135,6 +135,7 @@ def errorreport : QF<"errorreport">;
 def idlout : QF<"idlout">;
 def ignore : QF<"ignore">;
 def maxilksize : QF<"maxilksize">;
+def natvis : QF<"natvis">;
 def pdbaltpath : QF<"pdbaltpath">;
 def tlbid : QF<"tlbid">;
 def tlbout : QF<"tlbout">;