Merge "Update the instruction for building recovery image on Pixels."

Quick turn-around testing

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    mm -j && m ramdisk-nodeps && m recoveryimage-nodeps

* Devices using recovery-as-boot (e.g. Pixels, which set BOARD\_USES\_RECOVERY\_AS\_BOOT)

    # To boot into the new recovery image

    # without flashing the recovery partition:

      # After setting up environment and lunch.

      m -j bootimage

      adb reboot bootloader

      # Pixel devices don't support booting into recovery mode with `fastboot boot`.

      fastboot flash boot

      # Manually choose `Recovery mode` from bootloader menu.

* Devices with a separate recovery image (e.g. Nexus)

      # After setting up environment and lunch.

      mm -j && m ramdisk-nodeps && m recoveryimage-nodeps

      adb reboot bootloader

      # To boot into the new recovery image without flashing the recovery partition:

      fastboot boot $ANDROID_PRODUCT_OUT/recovery.img

Running the tests

-----------------

    # After setting up environment and lunch.

    mmma -j bootable/recovery

    # Running the tests on device.

    # Running the tests on device (under normal boot).

    adb root

    adb sync data