ppsspp/android/custom_rules.xml

<?xml version="1.0" encoding="UTF-8"?>
<project name="PPSSPP" default="help">
    <property name="ndkbuildopt" value=""/>
    <target name="-pre-build">
        <exec executable="${ndk.dir}/ndk-build" failonerror="true">
            <arg line="-j4 ${ndkbuildopt}"/>
            <env key="NDK_MODULE_PATH" path="..:../native/ext"/>
        </exec>
    </target>
    <target name="clean" depends="android_rules.clean">
        <exec executable="${ndk.dir}/ndk-build" failonerror="true">
            <arg value="clean"/>
            <env key="NDK_MODULE_PATH" path="..:../native/ext"/>
        </exec>
    </target>
</project>