lld-link: Add /lib to Options.td so that it appears in lld-link's help output.

[ruiu]

Can you add a test?

[thakis]

Sure, done.

[ruiu]

LGTM

[thakis]

r337086, thanks!

COFF/DriverUtils.cpp

opt::InputArgList ArgParser::parse(ArrayRef<const char *> Argv) {
 
   if (MissingCount)
     fatal(Twine(Args.getArgString(MissingIndex)) + ": missing argument");
 
   handleColorDiagnostics(Args);
 
   for (auto *Arg : Args.filtered(OPT_UNKNOWN))
     warn("ignoring unknown argument: " + Arg->getSpelling());
+
+  if (Args.hasArg(OPT_lib))
+    warn("ignoring /lib since it's not the first argument");
+
   return Args;
 }
 
 // Tokenizes and parses a given string as command line in .drective section.
 // /EXPORT options are processed in fastpath.
 std::pair<opt::InputArgList, std::vector<StringRef>>
 ArgParser::parseDirectives(StringRef S) {
   std::vector<StringRef> Exports;

COFF/Options.td

def errorlimit : P<"errorlimit",
     "Maximum number of errors to emit before stopping (0 = no limit)">;
 def export  : P<"export", "Export a function">;
 // No help text because /failifmismatch is not intended to be used by the user.
 def failifmismatch : P<"failifmismatch", "">;
 def guard   : P<"guard", "Control flow guard">;
 def heap    : P<"heap", "Size of the heap">;
 def ignore : P<"ignore", "Specify warning codes to ignore">;
 def implib  : P<"implib", "Import library name">;
+def lib : F<"lib">,
+    HelpText<"Act like lib.exe; must be first argument if present">;
 def libpath : P<"libpath", "Additional library search path">;
 def linkrepro : P<"linkrepro", "Dump linker invocation and input files for debugging">;
 def lldltocache : P<"lldltocache", "Path to ThinLTO cached object file directory">;
 def lldltocachepolicy : P<"lldltocachepolicy", "Pruning policy for the ThinLTO cache">;
 def lldsavetemps : F<"lldsavetemps">,
     HelpText<"Save temporary files instead of deleting them">;
 def machine : P<"machine", "Specify target platform">;
 def merge   : P<"merge", "Combine sections">;