Thanks to the instructions of @fabrizio.lombardozzi i could (with a minor change) compile the patched version successfully. His instructions were invaluable. 
:
sudo apt install mate-common libglib2.0-dev build-essential libgtk-3-dev libxml2-dev libxml2-dev libsoup2.4-dev libsoup3.0-dev libxml2-utils autopoint
wget https://github.com/mate-desktop/libmateweather/archive/refs/heads/master.zip
unzip master.zip
cd libmateweather-master/
./autogen.sh && ./configure --prefix=/usr --libdir=/usr/lib/x86_64-linux-gnu && make -j 4 && sudo make install
To load the new created version, kill clock-applet or logout and login again.