SDL: Don't define backends if SDL_GPU_DISABLED is set

SDL Commits
1 
From bc9780299c02e80eb0bfdb528367ed3a09fe948c Mon Sep 17 00:00:00 2001
From: Sam Lantinga <[EMAIL REDACTED]>
Date: Tue, 17 Sep 2024 09:00:57 -0700
Subject: [PATCH] Don't define backends if SDL_GPU_DISABLED is set

---
 src/gpu/SDL_gpu.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/src/gpu/SDL_gpu.c b/src/gpu/SDL_gpu.c
index 2c09f1671dff9..02a5eb23cd2e1 100644
--- a/src/gpu/SDL_gpu.c
+++ b/src/gpu/SDL_gpu.c
@@ -150,6 +150,7 @@
 
 // Drivers
 
+#ifndef SDL_GPU_DISABLED
 static const SDL_GPUBootstrap *backends[] = {
 #ifdef SDL_GPU_METAL
     &MetalDriver,
@@ -165,6 +166,7 @@ static const SDL_GPUBootstrap *backends[] = {
 #endif
     NULL
 };
+#endif // !SDL_GPU_DISABLED
 
 // Internal Utility Functions
 
@@ -547,7 +549,11 @@ void SDL_DestroyGPUDevice(SDL_GPUDevice *device)
 
 int SDL_GetNumGPUDrivers(void)
 {
+#ifndef SDL_GPU_DISABLED
     return SDL_arraysize(backends) - 1;
+#else
+    return 0;
+#endif
 }
 
 const char * SDL_GetGPUDriver(int index)