Fix Linux build

Author: squidbus

CMakeLists.txt

@@ -23,6 +23,10 @@ if (APPLE)
     enable_language(OBJC OBJCXX)
 endif()
 
+if (CMAKE_SYSTEM_NAME MATCHES "Linux")
+    set(SDL_VULKAN_ENABLED "ON")
+endif()
+
 if (CMAKE_OSX_ARCHITECTURES)
     set(MARATHON_RECOMP_ARCHITECTURE ${CMAKE_OSX_ARCHITECTURES})
 elseif(CMAKE_SYSTEM_PROCESSOR)

MarathonRecomp/CMakeLists.txt

@@ -374,7 +374,7 @@ if (MARATHON_RECOMP_METAL)
     target_compile_definitions(MarathonRecomp PRIVATE MARATHON_RECOMP_METAL)
 endif()
 
-if (CMAKE_SYSTEM_NAME MATCHES "Linux")
+if (SDL_VULKAN_ENABLED)
     target_compile_definitions(MarathonRecomp PRIVATE SDL_VULKAN_ENABLED)
 endif()