POSIX_SPAWN_* flags have incorrect type #3627

The following flags are defined as type c_int, even though the posix_spawnattr_setflags function demands that flags be of type c_short:

• POSIX_SPAWN_SETSID
• POSIX_SPAWN_RESETIDS
• POSIX_SPAWN_USEVFORK
• POSIX_SPAWN_SETPGROUP
• POSIX_SPAWN_SETSIGDEF
• POSIX_SPAWN_SETSIGMASK
• POSIX_SPAWN_SETSCHEDULER
• POSIX_SPAWN_SETSCHEDPARAM

See function signature here: https://docs.rs/libc/latest/libc/fn.posix_spawnattr_setflags.html