sdl12-compat: Turn of Visual C's silly C runtime warnings in SDLmain.

SDL Commits
1 
From b1c825d2b452307db593c9ff97ea5c93a549ebea Mon Sep 17 00:00:00 2001
From: "Ryan C. Gordon" <[EMAIL REDACTED]>
Date: Thu, 24 Jun 2021 15:42:35 -0400
Subject: [PATCH] Turn of Visual C's silly C runtime warnings in SDLmain.

---
 CMakeLists.txt | 1 +
 1 file changed, 1 insertion(+)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 8f1ea32..14c252a 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -110,6 +110,7 @@ if(APPLE)
     add_library(SDLmain STATIC src/SDLmain/macosx/SDLmain.m)
 elseif(WIN32)
     add_library(SDLmain STATIC src/SDLmain/win32/SDL_win32_main.c)
+    set_target_properties(SDLmain PROPERTIES COMPILE_DEFINITIONS "$_CRT_SECURE_NO_WARNINGS;_CRT_SECURE_NO_DEPRECATE;_CRT_NONSTDC_NO_DEPRECATE")  # !!! FIXME: don't use C runtime? We fixed this in SDL2.
 else()
     add_library(SDLmain STATIC src/SDLmain/dummy/SDL_dummy_main.c)
 endif()