tool/run: fix corner case in exit override

The run tool overrides the 'exit'-procedure to make sure that a loaded
run_power_off procedure is always executed. However, a failing
run_power_off lead to false-positives: 'make run/...' exited with 0 even
tough the run script was not even executed because of a failed
power-on/off cycle. In this case, if the run_power_off is the exit code
producer, the new exit definition does not finish as intended. As a
result, the first exit code is re-written, and errors are not propagated
accordingly.

The solution is to catch possible errors from power-off within the exit
procedure.

Fixes genodelabs#5102

tool/run/run

@@ -958,7 +958,7 @@ proc have_include { name } {
 #
 rename exit real_exit
 proc exit {{status 0}} {
-	run_power_off
+	catch {run_power_off}
 
 	real_exit $status
 }