Our current relocation works by invoking the dynamic linker with the
executable as an argument. This confuses gdb since the kernel records
the dynamic linker as the executable, not the real executable.
Switch to install-time relocation with patchelf: when installing the
executable and libraries, all paths are known, and we can update the
path to the dynamic loader and to the dynamic libraries.
Since patchelf itself is dynamically linked, we have to relocate it
dynamically (with the old method of invoking it via the dynamic linker).
This is okay since it's a one-time operation and since we don't expect
to debug core dumps of patchelf crashes.
We lose the ability to run scylla directly from the uninstalled
tarball, but since the nonroot installer is already moving in the
direction of requiring install.sh, that is not a great loss, and
certainly the ability to debug is more important.
dh_strip barfs on some binaries which were treated with patchelf,
so exclude them from dh_strip. This doesn't lose any functionality,
since these binaries didn't have debug information to begin with
(they are already-stripped Fedora executables).
Fixes#4673.
698b72b501