Fix linux build

Closes #17

CMakeLists.txt

@@ -10,7 +10,7 @@ set(CMAKE_CXX_STANDARD 17)
 set(CMAKE_CXX_STANDARD_REQUIRED YES)
 set(CMAKE_CXX_EXTENSIONS NO)
 
-add_executable(${EXECUTABLE_NAME} WIN32
+add_executable(${EXECUTABLE_NAME}
     "src/actions.cc"
     "src/actions.h"
     "src/animation.cc"
@@ -259,7 +259,7 @@ add_subdirectory("third_party/fpattern")
 target_link_libraries(${EXECUTABLE_NAME} ${FPATTERN_LIBRARY})
 target_include_directories(${EXECUTABLE_NAME} PRIVATE ${FPATTERN_INCLUDE_DIR})
 
-if(NOT APPLE)
+if(NOT APPLE AND NOT ${CMAKE_SYSTEM_NAME} MATCHES "Linux")
     add_subdirectory("third_party/zlib")
     add_subdirectory("third_party/sdl2")
 else()

src/core.cc

@@ -15,7 +15,9 @@
 #include <limits.h>
 #include <string.h>
 #include <SDL.h>
+#if _WIN32
 #include <SDL_syswm.h>
+#endif
 
 // NOT USED.
 void (*_idle_func)() = NULL;