Add build instructions to doxygen documentation (#1218)
Add build instructions to doxygen documentation (#1218)

* Add build instructions for doxygen docs

* Update build instructions to remove references to http demos

* Update formatting and add changes from other PRs

* Add @section for prerequisites

* Remove doxygen section
aws/aws-iot-device-sdk-embedded-C,aws/aws-iot-device-sdk-embedded-C,aws/aws-iot-device-sdk-embedded-C