foc: relax parsing of boot process termination

Until now, the successful termination of the boot process was recognized
when 'expect' saw the first L4 bootstrapper output on serial line. On sytems
with initially shaky serial connection like Versatile Express, where the serial
line baudrate changes with the bootstrapper initialization, the first expected
line might be missing. Therefore, change the expected line to the first
Fiasco.OC kernel output.

repos/base-foc/run/env

@@ -291,7 +291,7 @@ proc run_genode_until {{wait_for_re forever} {timeout_value 0} {running_spawn_id
 		return
 	}
 	if {[is_serial_available]} {
-		spawn_serial $wait_for_re $timeout_value "L4 Bootstrapper"
+		spawn_serial $wait_for_re $timeout_value "Welcome to Fiasco.OC"
 		return
 	}