in pathconf, -1, not 0, means unsupported.. syncio presumably works, too.
[musl] / arch / i386 /
drwxr-xr-x   ..
-rw-r--r-- 2801 atomic.h
drwxr-xr-x - bits
-rw-r--r-- 195 pthread_arch.h
-rw-r--r-- 672 reloc.h