Sdl12-compat: use 'set_target_properties' instead of 'add_definitions'

SDL Commits
1 
From dfa12b8cf429f028dd91812f0f38bf74ace65c37 Mon Sep 17 00:00:00 2001
From: Ozkan Sezer <[EMAIL REDACTED]>
Date: Tue, 23 Feb 2021 14:10:02 +0300
Subject: [PATCH] use 'set_target_properties' instead of 'add_definitions'

---
 CMakeLists.txt | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 3713c38..7f44049 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -25,11 +25,11 @@ if(WIN32)
 endif()
 
 if(UNIX AND NOT APPLE)
-    add_definitions("-D_REENTRANT")
+    set_target_properties(SDL PROPERTIES COMPILE_DEFINITIONS "_REENTRANT")
     target_link_libraries(SDL PRIVATE dl)
 endif()
 if(APPLE)
-    add_definitions("-D_THREAD_SAFE")
+    set_target_properties(SDL PROPERTIES COMPILE_DEFINITIONS "_THREAD_SAFE")
     target_link_libraries(SDL PRIVATE "-framework AppKit")
 endif()