[gn build] Port 428ffbd

Author: llvmgnsyncbot

llvm/utils/gn/secondary/lldb/tools/lldb-dap/BUILD.gn

@@ -44,6 +44,7 @@ static_library("lib") {
     "Handler/InitializeRequestHandler.cpp",
     "Handler/LaunchRequestHandler.cpp",
     "Handler/LocationsRequestHandler.cpp",
+    "Handler/ModuleSymbolsRequestHandler.cpp",
     "Handler/ModulesRequestHandler.cpp",
     "Handler/NextRequestHandler.cpp",
     "Handler/PauseRequestHandler.cpp",