libwebsockets

cmake force internal SHA1 if no ssl

https://github.com/warmcat/libwebsockets/issues/342

You have to explicitly disable LWS_WITHOUT_BUILTIN_SHA1 Cmake option
alomg with SSL to disable SSL

cmake .. -DLWS_WITH_SSL=OFF -DLWS_WITHOUT_BUILTIN_SHA1=OFF

This makes that implicit with disabling SSL.

Signed-off-by: Andy Green <andy.green@linaro.org>