packaging: move Inno Setup core logic into a module Aspects of building the Inno Setup and WIX installers are shared. It will make sense for them to share code. Plus, having code in a reusable library (as opposed to a standalone script) is just a better approach. This commit moves the core logic to build the Inno Setup installer into the hgpackaging package. inno/build.py is now a simple frontend script that calls into a module to do the bulk of the work. As part of this change, I also found a typo in build() where it was referencing "iscc" instead of "iscc_exe." Because "iscc" was in the global scope via the only caller, things just happened to work before. Another benefit of always using functions and not putting global code for __main__ in the same file as library code. Differential Revision: https://phab.mercurial-scm.org/D6087

--- a/tests/test-check-code.t	Thu Mar 07 10:22:09 2019 -0800
+++ b/tests/test-check-code.t	Thu Mar 07 15:43:14 2019 -0800
@@ -13,6 +13,7 @@
   > -X mercurial/thirdparty \
   > | sed 's-\\-/-g' | "$check_code" --warnings --per-file=0 - || false
   Skipping contrib/packaging/hgpackaging/downloads.py it has no-che?k-code (glob)
+  Skipping contrib/packaging/hgpackaging/inno.py it has no-che?k-code (glob)
   Skipping contrib/packaging/hgpackaging/util.py it has no-che?k-code (glob)
   Skipping contrib/packaging/inno/build.py it has no-che?k-code (glob)
   Skipping i18n/polib.py it has no-che?k-code (glob)