SDL: quit: don't call signal() if we're using sigaction() (c6363)

SDL Commits
1 
From c636332031b530d5c8cd79569d76f4fe7ed53f0c Mon Sep 17 00:00:00 2001
From: Cameron Gutman <[EMAIL REDACTED]>
Date: Mon, 1 Dec 2025 17:31:55 -0600
Subject: [PATCH] quit: don't call signal() if we're using sigaction()

At best, this is a no-op.

At worst, it might:
 - Clobber a signal handler someone registered after us
 - Overwrite the signal mask or flags
 - Cause unregistration to fail (sigaction() isn't guaranteed to return the exact pointer passed to signal())

(cherry picked from commit 1d852d1c2872ec4275505e10e0e02392c0d60405)
---
 src/events/SDL_quit.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/events/SDL_quit.c b/src/events/SDL_quit.c
index b4234fc2185c6..dcf722645c8a4 100644
--- a/src/events/SDL_quit.c
+++ b/src/events/SDL_quit.c
@@ -49,8 +49,10 @@ static SDL_bool send_foregrounding_pending = SDL_FALSE;
 
 static void SDL_HandleSIG(int sig)
 {
-    /* Reset the signal handler */
+#ifndef HAVE_SIGACTION
+    /* Reset the signal handler if it was installed with signal() */
     (void)signal(sig, SDL_HandleSIG);
+#endif
 
     /* Send a quit event next time the event loop pumps. */
     /* We can't send it in signal handler; SDL_malloc() might be interrupted! */