roi_harness: write design.txt into output dir

Signed-off-by: John McMaster <johndmcmaster@gmail.com>

minitests/roi_harness/runme.tcl

diff --git a/minitests/roi_harness/runme.tcl b/minitests/roi_harness/runme.tcl
index b8b1239..ebe2893 100644
--- a/minitests/roi_harness/runme.tcl
+++ b/minitests/roi_harness/runme.tcl
@@ -350,7 +350,7 @@
 }
 
 # XXX: maybe add IOB?
-set fp [open "design.txt" w]
+set fp [open "$outdir/design.txt" w]
 puts $fp "name node pin"
 # Manual routing
 if {$fixed_xdc eq ""} {