[modules] Frontend support for building a header module from a list of
headaer files.

llvm-svn: 342304
diff --git a/clang/lib/Frontend/CompilerInvocation.cpp b/clang/lib/Frontend/CompilerInvocation.cpp
index b11581d..55745b1 100644
--- a/clang/lib/Frontend/CompilerInvocation.cpp
+++ b/clang/lib/Frontend/CompilerInvocation.cpp
@@ -1454,6 +1454,8 @@
       Opts.ProgramAction = frontend::GenerateModule; break;
     case OPT_emit_module_interface:
       Opts.ProgramAction = frontend::GenerateModuleInterface; break;
+    case OPT_emit_header_module:
+      Opts.ProgramAction = frontend::GenerateHeaderModule; break;
     case OPT_emit_pch:
       Opts.ProgramAction = frontend::GeneratePCH; break;
     case OPT_emit_pth:
@@ -2830,6 +2832,7 @@
   case frontend::FixIt:
   case frontend::GenerateModule:
   case frontend::GenerateModuleInterface:
+  case frontend::GenerateHeaderModule:
   case frontend::GeneratePCH:
   case frontend::GeneratePTH:
   case frontend::ParseSyntaxOnly: