Revert "Do not use Phive to manage php-cs-fixer (for now)"

This reverts commit 6d8b244.

build.xml

@@ -398,10 +398,6 @@
         <exec executable="${basedir}/build/tools/composer">
             <arg value="self-update"/>
         </exec>
-
-        <exec executable="${basedir}/build/tools/php-cs-fixer" taskname="php-cs-fixer" failonerror="true">
-            <arg value="selfupdate"/>
-        </exec>
     </target>
 
     <target name="-phploc" depends="prepare">

phive.xml

@@ -1,6 +1,7 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <phive xmlns="https://phar.io/phive">
   <phar name="phpab" version="^1.24.1" installed="1.25.1" location="./build/tools/phpab" copy="true"/>
+  <phar name="php-cs-fixer" version="^2.12.0" installed="2.13.2" location="./build/tools/php-cs-fixer" copy="true"/>
   <phar name="phpdox" version="^0.11.2" installed="0.11.2" location="./build/tools/phpdox" copy="true"/>
   <phar name="phploc" version="^4.0.1" installed="4.0.1" location="./build/tools/phploc" copy="true"/>
 </phive>