ModuleInterface: make -public-module-name an ignorable flag

Author: xymus

include/swift/Option/Options.td

@@ -580,7 +580,7 @@ def export_as : Separate<["-"], "export-as">,
   Flags<[FrontendOption, ModuleInterfaceOption]>,
   HelpText<"Module name to use when referenced in clients module interfaces">;
 def public_module_name : Separate<["-"], "public-module-name">,
-  Flags<[FrontendOption, ModuleInterfaceOption]>,
+  Flags<[FrontendOption, ModuleInterfaceOptionIgnorable]>,
   HelpText<"Public facing module name to use in diagnostics and documentation">;
 
 def emit_module : Flag<["-"], "emit-module">,

test/Sema/public-module-name.swift

@@ -29,7 +29,8 @@
 /// Check flag in swiftinterface
 // RUN: cat %t/LibCore.swiftinterface | %FileCheck --check-prefix=CHECK-FLAG %s
 // RUN: cat %t/LibMiddle.swiftinterface | %FileCheck --check-prefix=CHECK-FLAG %s
-// CHECK-FLAG: -public-module-name Lib
+// CHECK-FLAG: swift-module-flags-ignorable:
+// CHECK-SAME-FLAG: -public-module-name Lib
 
 /// Build clients against binary swiftmodules.
 /// First errors in files, then diagnostics in other files.