Make heartbeat build without needing root

The solution was to call dh_fixperms, before calling dh_strip. This also matches dh own sequence. The only two commands affected by this change (beyond dh_strip) is:

• dh_compress: Ok. Next debhelper compat level will have dh run dh_compress after dh_fixperms, so this is fine.
• Manual stripping of static libraries: Ok as well, since strip is mode preserving. As an example, dh_strip does not manually reset the mode itself, so it stands to reason that the custom stripping here would not need to either.

Closes: #1089342