Regular-expression compatibility.

The most compatible way of indicating that a dash is part of a
character range is to put a single dash at the end of the range
expression.

Change-Id: I1e118038dfacffbc004c97be0ae1c3dfe97e861d
diff --git a/opcode-gen/opcode-gen.awk b/opcode-gen/opcode-gen.awk
index 0b14a3f..9280ed2 100644
--- a/opcode-gen/opcode-gen.awk
+++ b/opcode-gen/opcode-gen.awk
@@ -48,8 +48,8 @@
 }
 
 # Detect directives.
-/BEGIN\([a-z---]*\)/ {
-    i = match($0, /BEGIN\([a-z---]*\)/);
+/BEGIN\([a-z-]*\)/ {
+    i = match($0, /BEGIN\([a-z-]*\)/);
     emission = substr($0, i + 6, RLENGTH - 7);
     consumeUntil = "END(" emission ")";
     emissionHandled = 0;