cmake: modernize lib target specification
cmake: modernize lib target specification

Use modern CMake idioms when defining rabbitmq and rabbitmq-static
library targets.

Signed-off-by: GitHub <1505422b2465e9a84f6fdfaa161078890c593f06@github.com>

alanxz/rabbitmq-c,alanxz/rabbitmq-c,alanxz/rabbitmq-c