tests: Use readdir64 when _FILE_OFFSET_BITS set
tests: Use readdir64 when _FILE_OFFSET_BITS set

On 32 bit systems, _FILE_OFFSET_BITS will be set to 64 by
AC_SYS_LARGEFILE. This causes the glibc headers to use readdir64 rather
than readdir. Emulate that behavior in the preloader or the tests will
all fail with "No such file or directory".

leandrosansilva/ostree,gatispaeglis/ostree,GNOME/ostree,GNOME/ostree,gatispaeglis/ostree,sujitfulse/ostree,GNOME/ostree,leandrosansilva/ostree,sujitfulse/ostree,gatispaeglis/ostree,leandrosansilva/ostree,leandrosansilva/ostree,gatispaeglis/ostree,gatispaeglis/ostree,GNOME/ostree,sujitfulse/ostree,leandrosansilva/ostree,gatispaeglis/ostree,GNOME/ostree,sujitfulse/ostree,sujitfulse/ostree