[modules] Add include/llvm/IR/DebugInfoFlags.def to the textual headers list.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@230427 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/module.modulemap

@@ -108,6 +108,7 @@ module LLVM_IR {
   module * { export * }
 
   // These are intended for (repeated) textual inclusion.
+  textual header "IR/DebugInfoFlags.def"
   textual header "IR/Instruction.def"
   textual header "IR/Metadata.def"
 }