Try to fix mysterious __sleep crash

We're seeing that some opt builds crash if you throw from
__sleep. After a lot of debugging, it looks like the eh_frame section
contains a bogus entry for php_sleep (in addition to the correct one),
and eh_frame_hdr's entry points to the wrong one (if I intervene in
gdb and point it to the right one, everything works).

I'm pretty sure this is a bug in gold (the eh_frame data appears
to be correct in object_data.o), and changes to unrelated code
make the bug appear and disappear.

I'm not sure exactly what the issue is, but php_sleep is basically a
hangover from hphpc days, so I'm killing it (and modifying the meaning
of HasSleep slightly - it now means what you expect). Not very satisfying
but hopefully it will work...

Differential Revision: D906292
Fix handling of "not buildling from git" case

The fallback for repo-schema and compiler-id
generation when not building from git was to use the system
microtime.  Unfortunately, using a '.' in the repo-schema
leads to bad SQL table names.  Use an underscore instead.

Differential Revision: D906623