run: use 'wait_for_output' for Linux, too

With this patch, the Linux-specific 'run_genode_until' function uses
'wait_for_output' as it gets already used for other run targets.

Fixes #863.

base-linux/run/env

@@ -35,18 +35,13 @@ proc run_genode_until {{wait_for_re forever} {timeout_value 0} {running_spawn_id
 		return
 	}
 
-	global output
-	set timeout $timeout_value
+	global spawn_id
+
 	set orig_pwd [pwd]
 	cd [run_dir]
-	set pid [spawn ./core]
-	if {$wait_for_re == "forever"} { interact $pid }
-	expect {
-		-re $wait_for_re { }
-		timeout { puts stderr "Error: Test execution timed out"; exit -2 }
-	}
+	spawn ./core
+	wait_for_output $wait_for_re $timeout_value $spawn_id
 	cd $orig_pwd
-	set output $expect_out(buffer)
 }