We need to build with
-DSHA1DC_FORCE_LITTLEENDIAN
to avoid a portability problem with endian detection in git 2.13.1:
https://public-inbox.org/git/xmqqmv9l8h5z.fsf@gitster.mtv.corp.google.com/t/
We actually call this version 2.13.1.2 to force apt to consider it
a higher version - it's a temporary lie until 2.13.2 is available.