1. Shared lib extension is .dll
2. Shared libs are installed to $(prefix)/bin
3. Linker does not support -z flag

3.81 doesn't understand the ‘define foo =’ syntax, which was added in
3.82.  So use ‘define foo’ instead.

This makes it easier to use with "git subtree".

Source: http://blog.jgc.org/2011/07/gnu-make-recursive-wildcard-function.html

This way, we can use config.status for generating scripts/* (without
ending up with lines like "#! /usr/bin/perl -I${libexecdir}/...").