SDL: cmake: Don't support Vulkan if LOADSO is disabled.

From 374b0b9aaff66bfacc80b20d2374555ea17a6e33 Mon Sep 17 00:00:00 2001
From: "Ryan C. Gordon" <[EMAIL REDACTED]>
Date: Mon, 23 Aug 2021 23:58:54 -0400
Subject: [PATCH] cmake: Don't support Vulkan if LOADSO is disabled.

Fixes #4373.
---
 CMakeLists.txt | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 72f62d0071..d3467f79ad 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -2249,6 +2249,11 @@ elseif(VITA)
 
 endif()
 
+if(VIDEO_VULKAN AND NOT SDL_LOADSO)
+  message(STATUS "Vulkan support is available, but disabled because there's no loadso.")
+  set(VIDEO_VULKAN OFF)
+endif()
+
 if(VIDEO_VULKAN)
   set(SDL_VIDEO_VULKAN 1)
   set(HAVE_VIDEO_VULKAN TRUE)