chore(lua): Use PACKAGE_DATADIR and AM_CPPFLAGS

src/Makefile.am

@@ -196,4 +196,4 @@ libsub_root_a_SOURCES = \
 	thread_worker.h
 
 
-AM_CPPFLAGS = -I$(srcdir) -I$(top_srcdir)
+AM_CPPFLAGS = -I$(srcdir) -I$(top_srcdir) -DPACKAGE_DATADIR=\"$(pkgdatadir)\"

src/rpc/lua.cc

@@ -23,12 +23,12 @@
 
 namespace rpc {
 
+#ifdef HAVE_LUA
+
 const int         LuaEngine::flag_string;
 const std::string LuaEngine::module_name = "rtorrent";
 const std::string LuaEngine::local_path = LUA_DATADIR "/?.lua;" LUA_DATADIR "/?/init.lua";
 
-#ifdef HAVE_LUA
-
 LuaEngine::LuaEngine() {
   m_luaState = luaL_newstate();
   luaL_openlibs(m_luaState);

src/rpc/lua.h

@@ -6,6 +6,7 @@
 
 #ifdef HAVE_LUA
 #include <lua.hpp>
+#define LUA_DATADIR PACKAGE_DATADIR "/lua"
 #endif
 
 namespace rpc {