title: make -j (jobs) option ignored when building Android (defaulting to all cores)
body: <p>I'm building Android-x86 (the <code>nougat-x86</code> branch) with this sequence of commands:</p>
  
  <pre class="lang-bsh prettyprint-override"><code>repo init -u git://git.osdn.net/gitroot/android-x86/manifest -b nougat-x86
  
  repo sync --no-tags --no-clone-bundle
  
  virtualenv2 venv
  
  . venv/bin/activate
  
  . build/envsetup.sh
  
  lunch android_x86_64-userdebug
  
  export ANDROID_JACK_VM_ARGS="-Xmx4g -XX:+TieredCompilation -Dfile.encoding=UTF-8"
  export JACK_SERVER_VM_ARGUMENT=$ANDROID_JACK_VM_ARGS
  export SERVER_NB_COMPILE=1
  export USE_CCACHE=1
  
  LANG=C LC_ALL=C make -j2 iso_img
  </code></pre>
  
  <p>Note how I'm specifying two make jobs with option <code>-j2</code> at the last line.</p>
  
  <p>Regardless, the build is actually spawning 8 processes of <code>clang</code> / <code>clang++</code> / <code>javac</code> and whatever else.</p>
  
  <p>This causes the build to fail:</p>
  
  <blockquote>
    <p>GC overhead limit exceeded<br>
    Try increasing heap size with java option '-Xmx'<br>
    Warning: This may have produced partial or corrupted output.<br>
    ninja: build stopped: subcommand failed.<br>
    make: *** [ninja_wrapper] Error 1  </p>
    
    make failed to build some targets
  </blockquote>
  
  <p><br>
  How to enforce the <code>-j2</code> option to make sure my CPU and RAM are not maxed out?</p>