Remnant build-only dependencies.

[victorusu]

This is a feature request.

When building software, one may face the installation of build-only dependencies that are not used anymore. These dependencies are good candidates to be removed.

One example is the installation of binutils

eb binutils-2.31.1.eb -Dr
.../m/M4/M4-1.4.18.eb
.../b/Bison/Bison-3.0.5.eb
.../z/zlib/zlib-1.2.11.eb
.../b/Bison/Bison-3.0.4.eb
.../h/help2man/help2man-1.47.4.eb
.../f/flex/flex-2.6.4.eb
.../b/binutils/binutils-2.31.1.eb

Bison here is not only installed twice, but the version 3.0.4 is a build-only dependency of flex, which has not been upgraded to a newer version since ages and old toolchains use the same flex recipe in the installation process. Newer versions of binutils use Bison version 3.0.5 as build-only dependency. Which is also not used anymore in the toolchain compilation.

These two Bison versions could be removed, since they just occupy space.