Set proper xdebug version (#7)

Author: rybakit

dockerfile.sh

@@ -13,8 +13,7 @@ if [[ $PHP_RUNTIME == php* ]]; then
 fi
 
 if [[ $PHPUNIT_OPTS =~ (^|[[:space:]])--coverage-[[:alpha:]] ]]; then
-    RUN_CMDS="$RUN_CMDS && \\\\\n    git clone https://github.com/xdebug/xdebug.git /usr/src/php/ext/xdebug"
-    RUN_CMDS="$RUN_CMDS && \\\\\n    echo xdebug >> /usr/src/php-available-exts && docker-php-ext-install xdebug"
+    RUN_CMDS="$RUN_CMDS && \\\\\n    pecl install xdebug && docker-php-ext-enable xdebug"
 fi
 
 echo -e "