vulkan: Set unused entrypoints to vk_entrypoint_stub when compiling with MSVC

If we don't do that we hit the assert(entry[i] != NULL) added by commit
6d44b21d4f ("vulkan: Fix weak symbol emulation when compiling with MSVC").

Fixes: 6d44b21d4f ("vulkan: Fix weak symbol emulation when compiling with MSVC")
Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
Reviewed-by: Jesse Natalie <jenatali@microsoft.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/13355>

src/vulkan/util/vk_dispatch_table_gen.py

@@ -68,6 +68,10 @@ TEMPLATE_H = Template(COPYRIGHT + """\
 extern "C" {
 #endif
 
+#ifdef _MSC_VER
+void vk_entrypoint_stub(void);
+#endif
+
 <%def name="dispatch_table(entrypoints)">
 % for e in entrypoints:
   % if e.alias:

src/vulkan/util/vk_entrypoints_gen.py

@@ -148,6 +148,8 @@ const struct vk_${type}_entrypoint_table ${p}_${type}_entrypoints = {
     % endif
     .${e.name} = ${p}_${e.name},
     % if e.guard is not None:
+#elif defined(_MSC_VER)
+    .${e.name} = (PFN_vkVoidFunction)vk_entrypoint_stub,
 #endif // ${e.guard}
     % endif
   % endfor