Add auto option to device size

Typically device size is determined first, and then lpmake checks if
given partitions fit to the device or not. But it could be the case that
one wants to minimize the super image size, like microdroid. This change
adds "--device-size=auto" option to support minimized super image. If
set, the device size will be the sum of partition sizes plus some spaces
for metadata.

Bug: 181107248
Test: boot microdroid
Change-Id: I441f996de10df58bcfeb6f6ee637f15360d3b709
1 file changed