SDL: cmake (CheckPTHREAD): remove _GNU_SOURCE define after bug #7026 fix (0d8c2)

From 0d8c22acd216748b6d8bef75bd5adc6fb8f7accc Mon Sep 17 00:00:00 2001
From: Ozkan Sezer <[EMAIL REDACTED]>
Date: Mon, 9 Jan 2023 01:30:37 +0300
Subject: [PATCH] cmake (CheckPTHREAD): remove _GNU_SOURCE define after bug
 #7026 fix

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

diff --git a/cmake/sdlchecks.cmake b/cmake/sdlchecks.cmake
index ee24d574ba71..8700441c4873 100644
--- a/cmake/sdlchecks.cmake
+++ b/cmake/sdlchecks.cmake
@@ -820,7 +820,6 @@ macro(CheckPTHREAD)
       list(APPEND SDL_PC_CFLAGS ${PTHREAD_CFLAGS})
 
       check_c_source_compiles("
-        #define _GNU_SOURCE 1
         #include <pthread.h>
         int main(int argc, char **argv) {
           pthread_mutexattr_t attr;
@@ -831,7 +830,6 @@ macro(CheckPTHREAD)
         set(SDL_THREAD_PTHREAD_RECURSIVE_MUTEX 1)
       else()
         check_c_source_compiles("
-            #define _GNU_SOURCE 1
             #include <pthread.h>
             int main(int argc, char **argv) {
               pthread_mutexattr_t attr;
@@ -862,7 +860,6 @@ macro(CheckPTHREAD)
       check_include_file(pthread_np.h HAVE_PTHREAD_NP_H)
       if (HAVE_PTHREAD_H)
         check_c_source_compiles("
-            #define _GNU_SOURCE 1
             #include <pthread.h>
             int main(int argc, char **argv) {
               pthread_setname_np(pthread_self(), \"\");