package/azure-iot-sdk-c: bump to version 2018-12-13

package/azure-iot-sdk-c: bump to version 2018-12-13

Bump azure-iot-sdk-c to 2018-12-13 release.

We need to specify a value for CMAKE_SYSTEM_VERSION, because the
azure-iot-sdk-c build system is doing a test on this value, and CMake
doesn't internally define it when cross-compiling (see
https://cmake.org/cmake/help/v3.4/variable/CMAKE_SYSTEM_VERSION.html).

Signed-off-by: Nikita Sobolev <Nikita.Sobolev@synopsys.com>
[Thomas: drop patch, pass dummy CMAKE_SYSTEM_VERSION instead.]
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>