Library Forwarding/vulkan: Fix query of vkCreateInstance function poi…

…nter

The Vulkan specification states that querying "global commands" like
vkCreateInstance with a non-NULL instance is undefined behavior. Indeed, some
implementations will return null pointers in such cases.

Instead, we can drop the query from DoSetupWithInstance altogether, since
the library initializer will load the function pointer using dlsym instead.

Fixes #3519.

ThunkLibs/libvulkan/Host.cpp

@@ -39,7 +39,6 @@ static void DoSetupWithInstance(VkInstance instance) {
     }
 
     // Query pointers for functions customized below
-    (void*&)LDR_PTR(vkCreateInstance) = (void*)LDR_PTR(vkGetInstanceProcAddr)(instance, "vkCreateInstance");
     (void*&)LDR_PTR(vkCreateDevice) = (void*)LDR_PTR(vkGetInstanceProcAddr)(instance, "vkCreateDevice");
 
     // Only do this lookup once.