#include_next doesn't find <sys/select.h>

On Alpine, the file /usr/include/fortify/sys/select.h gets included by the stdlib and contains #include_next <sys/select.h>. The file /usr/include/sys/select.h does exist. However, cc fails with:

/usr/include/fortify/sys/select.h:23:15: include file not found: <sys/select.h>

As seen in https://builds.sr.ht/~emersion/job/983460