Generate PNGs at build

[Thaodan]

Currently icons have to be generate separate which taints the build makes it non reproduce-able. If the conversion is done it build time this is solved. If we use SailfishOS to get the python3-cairosvg we can use that to generate the icons at build time (partialy already done in https://github.com/Huessenbergnetz/HBN_SFOS_Components/issues/1)

See here for reference how to generate icons:

• https://github.com/communi/communi-sailfish/blob/master/data/data.pro (its qmake but could work similar in cmake)

Python3-Cairosvg in chum:

• https://github.com/sailfishos-chum/python3-cairosvg
• https://build.sailfishos.org/package/show/sailfishos:chum/python3-cairosvg

[buschmann23]

Will implement this when switching to CMake.