packaging: install and run Inno files in a build directory
Upcoming commits will refactor the Windows installers so their
content is dynamically derived. In preparation for this, we
copy the Inno files into a new build directory and run them
from there. This required changing some relative paths to
work from a new directory level but is otherwise a pretty
straightforward change.
Differential Revision: https://phab.mercurial-scm.org/D7157
Our full contribution guidelines are in our wiki, please see:
https://www.mercurial-scm.org/wiki/ContributingChanges
If you just want a checklist to follow, you can go straight to
https://www.mercurial-scm.org/wiki/ContributingChanges#Submission_checklist
If you can't run the entire testsuite for some reason (it can be
difficult on Windows), please at least run `contrib/check-code.py` on
any files you've modified and run `python contrib/check-commit` on any
commits you've made (for example, `python contrib/check-commit
273ce12ad8f1` will report some style violations on a very old commit).