With the recovery image being installed by applypatch, the flash_image
tool isn't needed any more. Continue to build it for eng just in case
it's handy for debugging.
We fail to detect certain bad blocks (marked in the factory as bad, I
think?) when reading mtd partitions. These come back as a block of
all zeros. Since it's fairly unlikely a legitimate boot or recovery
block will contain 128k of zeros, change mtdutils to skip over such
blocks.
Arve says https://review.source.android.com/10535 may be a long-term
fix for this, but he isn't yet sure.
