Autoconf

Many open source packages use Autoconf for portability
Maintainer uses autoconf to generate configure script
User runs configure script to generate Makefile
  $ ./configure --target=mipsel-unknown-linux-gnu

Older configure scripts require overriding CC, e.g.
  $ CC=$target-gcc ./configure ...

Some configure scripts need hints, e.g.
  $ ac_cv_func_setpgrp_void=yes ./configure ...

It pays to understand configure scripts
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