packaging: stage installed files for Inno Previously, the Inno installer maintained its own mapping of source files to install location. (We have to maintain a similar mapping in the WiX installer.) Managing the explicit file layout for Windows packages is cumbersome and redundant. Every time you want to change the layout you need to change N locations. We frequently forget to do this and we only find out when people install Mercurial from our packages at release time. This commit starts the process of consolidating and simplifying the logic for managing the install layout on Windows. We introduce a list of install layout rules. These are simply source filenames (which can contain wildcards) and destination paths. The Inno packaging code has been updated to assemble all files into a staging directory that mirrors the final install layout. The list of files to add to the installer is derived by walking this staging directory and dynamically emitting the proper entries for the Inno Setup script. I diffed the file layout before and after this commit and there is no difference. Another benefit of this change is that it facilitates easier testing of the Windows install layout. Before, in order to test the final install layout, you needed to build an installer and run it. Now, you can stage files into the final layout and test from there, without running the installer. This should cut down on overhead when changing Windows code. Differential Revision: https://phab.mercurial-scm.org/D7159