kernel-install.eclass: run depmod after compressing modules

(de)compressing modules changes the path of the module files so we need to
run depmod to ensure that tools such as modprobe/modinfo work.

Note that depmod is often, but *not* always, run by sys-kernel/installkernel.
Systemd installs a hook to do this, but there is no equivalent on openrc
systems. So instead just ensure that the tree of modules we install is
consistent here in the eclass.

Signed-off-by: Andrew Ammerlaan <andrewammerlaan@gentoo.org>

eclass/kernel-install.eclass

@@ -796,6 +796,9 @@ kernel-install_compress_modules() {
 		find "${ED}/lib/modules/${KV_FULL}" -name '*.ko' -print0 |
 			xargs -0 -P "$(makeopts_jobs)" -n 128 "${compress[@]}"
 		assert "Compressing kernel modules failed"
+
+		# Module paths have changed, run depmod
+		depmod --all --basedir "${ED}" ${KV_FULL} || die
 	fi
 }