i386 does not support it https://buildd.debian.org/status/fetch.php?pkg=halide&arch=i386&ver=16.0.0-1&stamp=1689112307&raw=0

(Why is this not being handled at CMake time via check_cxx_source_compiles()?)

ppc64el/s390x does not support it either, but those builds never succeeded anyway...