Makefile: Fix certified version numbers

Adds sed before awk to produce reasonable ASTERISKVERSIONNUM
on certified versions of Asterisk eg. 16.8-cert3 is 160803
instead of the previous 00800.

ASTERISK-29021 #close

Change-Id: Icf241df0ff6db09011b8c936a317a84b0b634e16

Makefile

@@ -249,7 +249,7 @@ else
 endif
 ifneq ($(AWK),)
   ifneq ($(wildcard .version),)
-    ASTERISKVERSIONNUM:=$(shell $(AWK) -F. '{printf "%01d%02d%02d", $$1, $$2, $$3}' .version)
+    ASTERISKVERSIONNUM:=$(shell $(SED) -e 's/^certified\///' -e 's/-cert/./' .version | $(AWK) -F. '{printf "%01d%02d%02d", $$1, $$2, $$3}')
   endif
 endif