MQTT: take C part away from python code for readability.
C lines change a bit because of unnecessary escaping for '\'.
<?xml version='1.0' encoding='utf-8'?>
<BeremizRoot xmlns:xsd="http://www.w3.org/2001/XMLSchema" URI_location="LOCAL://">
<TargetType>
<Linux CFLAGS="-DBEREMIZ_TEST_CYCLES=1000"/>
</TargetType>
</BeremizRoot>