libwebsockets

linkit: support build using public sdk

This provides support to build lws using the linkit 7697 public SDK
from here https://docs.labs.mediatek.com/resource/mt7687-mt7697/en/downloads

This toolchain has some challenges, its int32_t / uint32_t are long,
so assumptions about format strings for those being %u / %d / %x all
break.  This fixes all the cases for the features enabled by the
default cmake settings.