[lldb] Fix warnings

This patch fixes:

  lldb/tools/lldb-rpc-gen/RPCCommon.cpp:197:13: error: unused variable
  'CheckTypeForLLDBPrivate' [-Werror,-Wunused-variable]

  lldb/tools/lldb-rpc-gen/lldb-rpc-gen.cpp:105:18: error: unused
  variable 'HasCallbackParameter' [-Werror,-Wunused-variable]

Author: kazutakahirata

lldb/tools/lldb-rpc-gen/RPCCommon.cpp

@@ -194,7 +194,6 @@ std::string lldb_rpc_gen::GetMangledName(ASTContext &Context,
   return Mangled;
 }
 
-static auto CheckTypeForLLDBPrivate = [](const Type *Ty) {};
 bool lldb_rpc_gen::TypeIsFromLLDBPrivate(QualType T) {
   auto CheckTypeForLLDBPrivate = [](const Type *Ty) {
     if (!Ty)

lldb/tools/lldb-rpc-gen/lldb-rpc-gen.cpp

@@ -102,8 +102,6 @@ class SBVisitor : public RecursiveASTVisitor<SBVisitor> {
           lldb_rpc_gen::GetMangledName(Context, MDecl);
       const bool IsDisallowed =
           lldb_rpc_gen::MethodIsDisallowed(Context, MDecl);
-      const bool HasCallbackParameter =
-          lldb_rpc_gen::HasCallbackParameter(MDecl);
       SupportLevel MethodSupportLevel = GetMethodSupportLevel(MDecl);
       if (MethodSupportLevel == eImplemented && !IsDisallowed) {
         const lldb_rpc_gen::Method Method(MDecl, Policy, Context);