Manual
VK_NO_STDDEF_H
Control definition of <stddef.h> types
If the VK_NO_STDDEF_H macro is defined by the application at compile
time, size_t, must also be defined by the application.
Otherwise, the Vulkan headers will not compile.
If VK_NO_STDDEF_H is not defined, the system <stddef.h> is used to
define this type.