Draft: testing/horizon: fix comparison for non x86 archs

/home/buildozer/aports/testing/horizon/src/horizon-0.9.6/./3rdparty/json.hpp:8494:24: error: comparison is always true due to limited range of data type [-Werror=type-limits]
 8494 |             if ('\x00' <= c and c <= '\x1F')
      |                 ~~~~~~~^~~~
[ 97%] Linking CXX executable hscript-image