automake problem

[[LoN]Kamikaze]

I'm trying to port a Firefox plugin that requires code from another
project, but autmake19 issues the following error message:

lib/Makefile.am:3: Libtool library used but `LIBTOOL' is undefined
lib/Makefile.am:3:
lib/Makefile.am:3: The usual way to define `LIBTOOL' is to add
`AC_PROG_LIBTOOL'
lib/Makefile.am:3: to `configure.in' and run `aclocal' and `autoconf' again.

I found this quite often on the web, but I either don't see or
understand offered solutions.