build: Fix libtool related warning
build: Fix libtool related warning

warning: 'libegglistbox.la': linking libtool libraries using a non-POSIX
archiver requires 'AM_PROG_AR' in 'configure.ac'

So add it before LT_INIT so it can be used by libtool

GNOME/egg-list-box,GNOME/egg-list-box,GNOME/egg-list-box