Ensure that -internal-import-bridging-header doesn't show up in a textual interface

Author: DougGregor

test/ClangImporter/InternalBridgingHeader/interface.swift

@@ -0,0 +1,14 @@
+// RUN: %empty-directory(%t)
+
+// RUN: %target-swift-emit-module-interface(%t/MyModule.swiftinterface) %s -module-name MyModule -internal-import-bridging-header %S/../Inputs/c-bridging-header.h -sdk %clang-importer-sdk -enable-library-evolution
+
+// RUN: %FileCheck %s < %t/MyModule.swiftinterface
+
+// CHECK-NOT: internal-import-bridging-header
+
+// CHECK: public func g()
+
+func getX(point: MyPoint) -> Double { point.x }
+
+public func g() {
+}