9.2 Hadrian does not install gen_contents_index

Summary

Hadrian installs of ghc 9.2 (including 9.2.5) don't include the libraries/gen_contents_index script.

This should be a pretty straightforward hadrian backport from 9.4.

(well I even pondered if I should try building 9.2 with 9.4 hadrian..)

Steps to reproduce

Install ghc-9.2 with Hadrian including haddocks.

Expected behavior

gen_contents_index should be installed like for make and 9.4 hadrian.

Environment

• GHC version used: 9.2.5

Optional:

• Operating System: Fedora Linux
• System Architecture: all

I marked this low priority since the functionality is not that critical, on the other hand it is a "breaking packaging change".