This was triggered by gcc for some reason It included sys/types.h and
assumed sys/select.h to be there. And that seams to be the case in musl.

The problem with relibc here is that sys/types.h is are part of relibc
"include/*.h" files, while sys/select.h is generated by cbindgen. That
makes it impossible to #include select.h in types.h epsecially that
there are files like fcntl.c that uses types.h. They would complain
about missing headers. I fixed this by renaming sys/types.h to
sys/types_internal.h and then generating types.h using cbindgen as well
except for that. however fcntl and dlmalloc can include types_internal
instead of types.h