[LLDB][NFC] treat Lua error codes in a more explicit manner

[tammela]

Summary

This patch is a minor suggestion to not rely on the fact
that the LUA_OK macro is 0.

This assumption could change in future versions of the C API.

[JDevlieghere]

LGTM

lldb/source/Plugins/ScriptInterpreter/Lua/Lua.cpp

 
 using namespace lldb_private;
 using namespace lldb;
 
 llvm::Error Lua::Run(llvm::StringRef buffer) {
   int error =
       luaL_loadbuffer(m_lua_state, buffer.data(), buffer.size(), "buffer") ||
       lua_pcall(m_lua_state, 0, 0, 0);
-  if (!error)
+  if (error == LUA_OK)
     return llvm::Error::success();
 
   llvm::Error e = llvm::make_error<llvm::StringError>(
       llvm::formatv("{0}\n", lua_tostring(m_lua_state, -1)),
       llvm::inconvertibleErrorCode());
   // Pop error message from the stack.
   lua_pop(m_lua_state, 1);
   return e;
llvm::Error Lua::LoadModule(llvm::StringRef filename) {
   ConstString module_extension = file.GetFileNameExtension();
   if (module_extension != ".lua") {
     return llvm::make_error<llvm::StringError>("invalid extension",
                                                llvm::inconvertibleErrorCode());
   }
 
   int error = luaL_loadfile(m_lua_state, filename.data()) ||
               lua_pcall(m_lua_state, 0, 1, 0);
-  if (error) {
+  if (error != LUA_OK) {
     llvm::Error e = llvm::make_error<llvm::StringError>(
         llvm::formatv("{0}\n", lua_tostring(m_lua_state, -1)),
         llvm::inconvertibleErrorCode());
     // Pop error message from the stack.
     lua_pop(m_lua_state, 1);
     return e;
   }