Issue #13725: regrtest does not recognize -d flag.

Patch by Erno Tukia.
diff --git a/Misc/ACKS b/Misc/ACKS
index 6ad3f8c..24f3f45 100644
--- a/Misc/ACKS
+++ b/Misc/ACKS
@@ -920,6 +920,7 @@
 John Tromp
 Jason Trowbridge
 Anthony Tuininga
+Erno Tukia
 Stephen Turner
 Theodore Turocy
 Bill Tutt