gitian: Make linux build of OpenSSL deterministic

OpenSSL was embedding a timestamp causing its build to be
non-deterministic.
Change deps-linux to be deterministic by using FAKETIME
as needed and disabling it when it gets in the way.
gitian: Make linux boost dependency completely deterministic

It appears that the output was different every time.

This doesn't affect the final bitcoind/bitcoin-qt, but is confusing
nevertheless.

Fix it by using FAKETIME and zipping files in deterministic order.
gitian: Sort generated source distribution archive

Sort the filenames in the resulting tar, normalize the time/date
and user/group information.
gitian: add -D flag to ar for deterministic output for linux deps

ar -D: Operate in deterministic mode. When adding files and the archive
index use zero for UIDs, GIDs, timestamps, and use consistent file modes
for all files.  When this option is used, if ar is used with identical
options and identical input files, multiple runs will create identical
output files regardless of the input files' owners, groups, file modes,
or modification times.