In general, the @TL{} build system uses the latest released versions of the @acronym{GNU} build tools, installed directly from the original @acronym{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 (@acronym{GNU} Autoconf) 2.69 automake (@acronym{GNU} automake) 1.14 ltmain.sh (@acronym{GNU} libtool) 2.4.2 bison (@acronym{GNU} Bison) 3.0 flex 2.5.37 m4 (@acronym{GNU} M4) 1.4.16 @end example