Add CMake switch for disabling Discord Rich Presence and fix no llvm build

3rdparty/CMakeLists.txt

@@ -152,7 +152,7 @@ target_include_directories(3rdparty_stblib INTERFACE stblib)
 add_library(3rdparty_discord-rpc INTERFACE)
 
 # We don't want Discord Rich Presence on the BSDs and other OSes
-if (WIN32 OR CMAKE_SYSTEM MATCHES "Linux" OR APPLE)
+if (USE_DISCORD_RPC AND (WIN32 OR CMAKE_SYSTEM MATCHES "Linux" OR APPLE))
 	if (WIN32 AND NOT MSVC)
 		ExternalProject_Add(discord-rpc
 				GIT_REPOSITORY https://github.com/discordapp/discord-rpc

3rdparty/llvm.cmake

@@ -1,4 +1,4 @@
-if(NOT WITHOUT_LLVM)
+if(WITH_LLVM)
 	if(BUILD_LLVM_SUBMODULE)
 		message(STATUS "LLVM will be built from the submodule.")