Remove hack in __gthread_active_p() to always return 0 on x86_64

Remove hack in __gthread_active_p() to always return 0 on x86_64

This was causing __cxa_guard_acquire to fail and abort if
two threads attempted to initialise the same static local
at same time.

It also presumably had other adverse effects in other
parts of the gcc standard libraries.

TEST= local testing + trybots
BUG= https://code.google.com/p/nativeclient/issues/detail?id=3948
R=mcgrathr@chromium.org

Committed: https://git.chromium.org/gitweb?p=native_client/nacl-gcc.git;a=commit;h=f80d6b9ee7f94755c697ffb7194fb01dd0c537dd

[Sam Clegg, 2015-01-09 16:51:34]

sbc@chromium.org changed reviewers:
+ mcgrathr@chromium.org

[Roland McGrath, 2015-01-09 19:07:23]

I don't see the trybot runs.

[Sam Clegg, 2015-01-09 19:21:14]

On 2015/01/09 19:07:23, Roland McGrath wrote:
> I don't see the trybot runs.

They don't show up on the issue with toolchain-git-try.sh (not sure why).

There are the links:

http://build.chromium.org/p/tryserver.nacl/builders/nacl-toolchain-precise64-...
http://build.chromium.org/p/tryserver.nacl/builders/nacl-toolchain-mac-newlib...
http://build.chromium.org/p/tryserver.nacl/builders/nacl-toolchain-win7-newli...
http://build.chromium.org/p/tryserver.nacl/builders/nacl-toolchain-precise64-...

[Roland McGrath, 2015-01-09 22:59:19]

lgtm

[Sam Clegg, 2015-01-10 09:57:55]

Committed patchset #2 (id:20001) manually as
f80d6b9ee7f94755c697ffb7194fb01dd0c537dd (presubmit successful).