um: allow not setting extra rpaths in the linux binary

[ Upstream commit 386093c68ba3e8bcfe7f46deba901e0e80713c29 ]

There doesn't seem to be any reason for the rpath being set in
the binaries, at on systems that I tested on. On the other hand,
setting rpath is actually harming binaries in some cases, e.g.
if using nix-based compilation environments where /lib & /lib64
are not part of the actual environment.

Add a new Kconfig option (under EXPERT, for less user confusion)
that allows disabling the rpath additions.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
Stable-dep-of: 846cfbeed09b ("um: Fix adding '-no-pie' for clang")
Signed-off-by: Sasha Levin <sashal@kernel.org>