compile_pkg: Really use latest stable release

compile_pkgs

@@ -63,7 +63,7 @@ set_target() {
 
 # Configuration variables
 OPENWRT_URL="https://git.openwrt.org/openwrt/openwrt.git" # OpenWRT git repository URL
-OPENWRT_BRANCH=master # Git reference used to checkout OpenWRT repository
+OPENWRT_BRANCH="openwrt-18.06" # Git reference used to checkout OpenWRT repository
 PUBLISH_BRANCH="hbk" # Target publish branch
 FORCE="" # Force build
 EVERYTHING="" # Set this variable to build all packages not only minimal set