add LoongArchTargetParser.def to LLVM_Utils module

Weinling Lu's change from https://reviews.llvm.org/D136146
fails to build with -DLLVM_ENABLE_MODULES=1 cmake builds
like the LLDB Incremental CI bot on greendragon; this entry
is sufficient to unblock that style of build, it seems.

llvm/include/llvm/module.modulemap

@@ -420,6 +420,7 @@ module LLVM_Utils {
     textual header "Support/RISCVTargetParser.def"
     textual header "Support/TargetOpcodes.def"
     textual header "Support/X86TargetParser.def"
+    textual header "Support/LoongArchTargetParser.def"
   }
 
   // This part of the module is usable from both C and C++ code.