abuild: avoid dupes in provides so:*

similar as commit b3174ba7 ("abuild: make sure we don't add dupes of
provides", Fri Jun 5 12:56:44 2015 +0000)

abuild.in

@@ -1077,7 +1077,8 @@ trace_apk_deps() {
 
 	echo "# automatically detected:" >> "$dir"/.PKGINFO
 	if [ -f "$dir"/.provides-so ]; then
-		sed 's/^\(.*\) \([0-9].*\)/provides = so:\1=\2/' "$dir"/.provides-so \
+		sed 's/^\(.*\) \([0-9].*\)/provides = so:\1=\2/' \
+			"$dir"/.provides-so | sort -u \
 			>> "$dir"/.PKGINFO
 	fi
 	if [ -f "$dir"/.provides-pc ]; then