Call the actual PHP script instead of a shell script

This allows interoperability with windows

build.xml

@@ -34,7 +34,7 @@
 
     <!-- Runs PHPUnit -->
     <target name="test">
-        <exec command="php vendor/bin/phpunit" passthru="true" checkreturn="true"/>
+        <exec command="php vendor/phpunit/phpunit/phpunit" passthru="true" checkreturn="true"/>
     </target>
 
     <target name="release">