Sdl12-compat: check __unix__ instead of unix

SDL Commits
1 
From 3d45321ab52c5158881ff927e6e71c64285daf3a Mon Sep 17 00:00:00 2001
From: Ozkan Sezer <[EMAIL REDACTED]>
Date: Sat, 20 Feb 2021 05:00:30 +0300
Subject: [PATCH] check __unix__ instead of unix

---
 src/SDL12_compat.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/SDL12_compat.c b/src/SDL12_compat.c
index 89bb7d0..c6e23a8 100644
--- a/src/SDL12_compat.c
+++ b/src/SDL12_compat.c
@@ -780,7 +780,7 @@ static EventQueueType *EventQueueAvailable = NULL;
     #define LoadSDL20Library() ((Loaded_SDL20 = LoadLibraryA(SDL20_LIBNAME)) != NULL)
     #define LookupSDL20Sym(sym) GetProcAddress(Loaded_SDL20, sym)
     #define CloseSDL20Library() { if (Loaded_SDL20) { FreeLibrary(Loaded_SDL20); Loaded_SDL20 = NULL; } }
-#elif defined(unix) || defined(__APPLE__)
+#elif defined(__unix__) || defined(__APPLE__)
     #include <dlfcn.h>
     #ifdef __APPLE__
     #define SDL20_LIBNAME "libSDL2-2.0.0.dylib"