In general, the @TL{} build system uses the latest released versions of the
GNU build tools, installed directly from the original GNU releases (e.g., by
building them with @* @ @ @ @code{configure --prefix=/usr/local/gnu} @* and
having @env{PATH} start with @file{/usr/local/gnu/bin}).  Currently these
are

@example
autoconf (GNU Autoconf) 2.69
automake (GNU automake) 1.14.1
ltmain.sh (GNU libtool) 2.4.2
bison (GNU Bison) 3.0.2
flex 2.5.39
m4 (GNU M4) 1.4.17
makeinfo (GNU texinfo) 5.2
@end example