SDL: Fixed build error (thanks @sezero!)

SDL Commits
1 
From ac5a61cd608cea3118fe581a9f8fffe67da29397 Mon Sep 17 00:00:00 2001
From: Sam Lantinga <[EMAIL REDACTED]>
Date: Thu, 25 Apr 2024 09:45:10 -0700
Subject: [PATCH] Fixed build error (thanks @sezero!)

---
 src/joystick/linux/SDL_sysjoystick.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/joystick/linux/SDL_sysjoystick.c b/src/joystick/linux/SDL_sysjoystick.c
index ea4413a2b24de..6409e66b78878 100644
--- a/src/joystick/linux/SDL_sysjoystick.c
+++ b/src/joystick/linux/SDL_sysjoystick.c
@@ -912,7 +912,9 @@ static void LINUX_ScanSteamVirtualGamepads(void)
     int num_virtual_gamepads = 0;
     int virtual_gamepad_slot;
     VirtualGamepadEntry *virtual_gamepads = NULL;
+#ifdef SDL_USE_LIBUDEV
     int class;
+#endif
 
     count = scandir("/dev/input", &entries, filter_entries, NULL);
     for (i = 0; i < count; ++i) {