/sbin/ldconfig is in libc-bin 2.15-0ubuntu10.
This file is owned by root:root, with mode 0o755.
The actual contents of the file can be viewed below.
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 | #!/bin/sh
if  test $# = 0							\
    && test x"$LDCONFIG_NOTRIGGER" = x				\
 && test x"$DPKG_MAINTSCRIPT_PACKAGE" != x			\
 && dpkg-trigger --check-supported 2>/dev/null			\
 && dpkg --compare-versions "$DPKG_RUNNING_VERSION" ge '1.14.5ubuntu10~~'
then
	if dpkg-trigger --no-await ldconfig; then
		if test x"$LDCONFIG_TRIGGER_DEBUG" != x; then
			echo "ldconfig: wrapper deferring update (trigger activated)"
		fi
		exit 0
	fi	
fi
exec /sbin/ldconfig.real "$@"
 |