package/squashfs: fix musl build

The build errors were not yet found by the autobuilders:

action.c: In function ‘name_fn’:
action.c:1911:29: error: ‘FNM_EXTMATCH’ undeclared (first use in this function)
     FNM_PATHNAME|FNM_PERIOD|FNM_EXTMATCH) == 0;)
                             ^
pseudo.c: In function ‘read_pseudo_def’:
pseudo.c:435:11: error: ‘S_IFBLK’ undeclared (first use in this function)
   mode |= S_IFBLK;
           ^

Signed-off-by: Bernd Kuhls <bernd.kuhls@t-online.de>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>