[Clang importer] Remove addition of -Werror=non-modular-include-in-framework-module

We shouldn't be stricter than Clang. Fixes rdar://104064443.

Author: DougGregor

lib/ClangImporter/ClangImporter.cpp

@@ -502,12 +502,6 @@ importer::getNormalInvocationArguments(
       "-fmodules",
       "-Xclang", "-fmodule-feature", "-Xclang", "swift"
   });
-  // Don't enforce strict rules when inside the debugger to work around search
-  // path problems caused by a module existing in both the build/install
-  // directory and the source directory.
-  if (!importerOpts.DebuggerSupport)
-    invocationArgStrs.push_back(
-        "-Werror=non-modular-include-in-framework-module");
 
   bool EnableCXXInterop = LangOpts.EnableCXXInterop;