extra/squid: make the helper scripts executable

some of the helper scripts in /usr/lib/squid did not have execute
permissions.

extra/squid/APKBUILD

@@ -3,7 +3,7 @@
 pkgname=squid
 pkgver=2.7.6
 _ver=2.7.STABLE6
-pkgrel=4
+pkgrel=5
 pkgdesc="A full-featured Web proxy cache server."
 url="http://www.squid-cache.org"
 install="squid.post-install"
@@ -86,6 +86,7 @@ build() {
 		"$pkgdir"/etc/logrotate.d/squid
 
 	mkdir -p "$pkgdir"/var/cache/squid "$pkgdir"/var/log/squid
+	chmod +x "$pkgdir"/usr/lib/squid/*
 }