We were passing around the common cflags and setting them for each library
or executable, but this is just a repetition given we can just use
add_project_arguments for this.
Meson files are normally using 4-spaces to indent and functions use first
parameter on the same line while others at next indentation level, not
following the parenthesis indentation.
So adapt libfprint to follow the meson standard.
These examples have not been ported. In addition, they are also not very
useful these days, as the demo application offers a much nicer view to
view images from a sensor.
