Add another .def file to module map to fix modules buildbot's displeasure.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@283498 91177308-0d34-0410-b5e6-96231b3b80d8

include/clang/module.modulemap

@@ -38,6 +38,7 @@ module Clang_Basic {
   textual header "Basic/BuiltinsSystemZ.def"
   textual header "Basic/BuiltinsWebAssembly.def"
   textual header "Basic/BuiltinsX86.def"
+  textual header "Basic/BuiltinsX86_64.def"
   textual header "Basic/BuiltinsXCore.def"
   textual header "Basic/DiagnosticOptions.def"
   textual header "Basic/LangOptions.def"