SDL: cmake: include_guard() is not needed

SDL Commits
1 
From d0b39890d29b40193d33b23364d49ec132add335 Mon Sep 17 00:00:00 2001
From: Anonymous Maarten <[EMAIL REDACTED]>
Date: Mon, 13 Feb 2023 04:55:26 +0100
Subject: [PATCH] cmake: include_guard() is not needed

---
 cmake/3rdparty.cmake | 2 --
 1 file changed, 2 deletions(-)

diff --git a/cmake/3rdparty.cmake b/cmake/3rdparty.cmake
index 3d1325deab49..37ac30b70b52 100644
--- a/cmake/3rdparty.cmake
+++ b/cmake/3rdparty.cmake
@@ -1,5 +1,3 @@
-include_guard()
-
 function(get_clang_tidy_ignored_files OUTVAR)
   set(3RD_PARTY_SOURCES
       # Public GL headers