Declare VulkanCustomDriverAllowedByOS() in the Vulkan-free header

DriverManagerScreen.cpp included VulkanLoader.h, which pulls in X11 on
Linux, whose Screen typedef clashes with our Screen class.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Common/GPU/Vulkan/VulkanDriverVars.h

@@ -15,3 +15,6 @@ struct AdrenoEnvVarDef {
 };
 
 const AdrenoEnvVarDef *GetAdrenoEnvVarDefs(int *count);
+
+// False where AdrenoTools' linker namespace tricks are known or suspected to break (Android 17 and its previews).
+bool VulkanCustomDriverAllowedByOS();

Common/GPU/Vulkan/VulkanLoader.h

@@ -282,9 +282,6 @@ struct VulkanExtensions {
 
 void VulkanApplyCustomDriverEnvVars(AdrenoEnvVar envVars);
 
-// False where AdrenoTools' linker namespace tricks are known or suspected to break (Android 17 and its previews).
-bool VulkanCustomDriverAllowedByOS();
-
 // Way to do a quick check before even attempting to load.
 void VulkanSetNativeLibDir(std::string_view nativeLibDir);
 bool VulkanMayBeAvailable();

UI/DriverManagerScreen.cpp

@@ -4,7 +4,6 @@
 #include "Common/System/Request.h"
 #include "Common/System/OSD.h"
 #include "Common/GPU/Vulkan/VulkanDriverVars.h"
-#include "Common/GPU/Vulkan/VulkanLoader.h"
 #include "Common/Log.h"
 #include "Common/StringUtils.h"
 #include "Common/UI/PopupScreens.h"