uClibc: enable utmp for shadow compatibility

uClibc: enable utmp for shadow compatibility

with the enabling of utmpx in busybox and uClibc it was noted that shadow
support for utmpx also needs utmp explicitly enabled in uclibc. this is
a workaround that might be removed once shadow properly supports
--enable-utmpx to check for utmpx configuration instead of utmp like
it does now

[YOCTO #8243]

(From OE-Core rev: 969158d63ba2c8e2e11af41c2a6d4f1aa5b0099f)

Signed-off-by: Bogdan-Alexandru Voiculescu <bogdanx.a.voiculescu@intel.com>
Signed-off-by: Benjamin Esquivel <benjamin.esquivel@linux.intel.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>