Modify the Makefiles to pass in the current git hash, which is embedded into the translated output.  As a side effect, it is also embedded into the Subzero translator binary.  This is useful for two reasons:

1. The PNaCl component update process is somewhat manual, making it tricky long after the fact to know exactly which revision was pushed, e.g. when trying to reproduce a bug or crash.

2. A translated binary can be inspected to make sure Chrome used the expected revision of Subzero.  (And also to verify that pnacl-sz was used rather than pnacl-llc.)

The revision string is suppressed for lit tests, because a number of tests seem overly strict about global initializer expectations.

BUG= none
R=jpp@chromium.org

Review URL: https://codereview.chromium.org/2218363002 .