Merge "Allow USE_GOMA=true without explicit USE_NINJA=true"

# Notice: this works only with Google's Goma build infrastructure.

ifneq ($(USE_GOMA),)

  # Check if USE_NINJA is defined because GNU make won't work well

  # with goma. Note this file is evaluated twice, once with

  # USE_NINJA=true by GNU make and once with USE_NINJA=false by kati

  # which is invoked by GNU make. So, we cannot test the value of

  # USE_NINJA.

  ifndef USE_NINJA

    $(error USE_GOMA=true works only with USE_NINJA=true)

  # Check if USE_NINJA is not false because GNU make won't work well

  # with goma. Note this file is evaluated twice, once by GNU make and

  # once by kati with USE_NINJA=false. We do this check in the former

  # pass.

  ifndef KATI

    ifeq ($(USE_NINJA),false)

      $(error USE_GOMA=true is not compatible with USE_NINJA=false)

    endif

  endif

  # Goma requires a lot of processes and file descriptors.