Fix if condition

Author: BanzaiMan

bin/compile-extension-memcached

@@ -4,7 +4,7 @@ set -o errexit
 source $(dirname $0)/compile-extensions-common
 
 function install_memcache() {
-	if [ $(lsb_release -cs) = 'precise' || $(lsb_release -cs) = 'trusty' ]; then
+	if [[ $(lsb_release -cs) = 'precise' || $(lsb_release -cs) = 'trusty' ]]; then
 		pushd /tmp
 		wget https://launchpad.net/libmemcached/1.0/1.0.18/+download/libmemcached-1.0.18.tar.gz
 		tar xzf libmemcached-1.0.18.tar.gz