this means we don't need to handle this in the buildtool at all.
Mhm, that would not work, it appears that I did a mistake when I wrote the meson part. I checked for the bswap function but I should have checked for the builtin. However if I do check it with the builtin check, then meson will use the has_builtin() so then both values would depend on that function. I even think that meson could not handle anything without available has_attribute ...