libwebsockets

LWS_WITH_MINIMAL_EXAMPLES: default-off build all minimal samples after lws for QA

This adds an lws cmake option that builds all the minimal examples as part of lws,
it's useful for QA.

It adds a macro to examples that depend on a particular lws configuration to understand
they should just null out their project definition in builds where the lws configuration
requirement is not met, and we are building as part of lws.

It also adapts all the example library additions to select the just-built-but-not-yet-installed
library in the case it is built as part of lws.  If built standalone, it now uses the cmake
platform-abstracted way to add the library requirement too.