Add ability to install into dest_dir that independed of install_dir

Currently omnibus-software install into prefix, that sometimes not needed,
this commit emulates DESTDIR makefile behaviour

Signed-off-by: Vasiliy Tolstov <v.tolstov@selfip.ru>
gems do not have the concept of installing to a build dir and running out of another one.  if that bindir argument to gem install is rendered in the binstubs to point at the ruby then when you invoke those then you will break those binstubs when you install them.  so what you'd need to validate is that on unix that the shebang lines are correct and would need to spin up a windows virt to make sure that you haven't broken the bat files on that side.  there's also a ton of work which is going on in all these repos and the appbundler repo to try to fix all the bat file problems on windows.