Merge "make USER limited to 6 characters when generating BF_BUILD_NUMBER"

  ifneq ($(filter eng.%,$(BUILD_NUMBER)),)

    # Trim down BUILD_FINGERPRINT: the default BUILD_NUMBER makes it easily exceed

    # the Android system property length limit (PROPERTY_VALUE_MAX=92).

    BF_BUILD_NUMBER := $(USER)$(shell $(DATE) +%m%d%H%M)

    BF_BUILD_NUMBER := $(shell echo $${USER:0:6})$(shell $(DATE) +%m%d%H%M)

  else

    BF_BUILD_NUMBER := $(BUILD_NUMBER)

  endif