[NaCl SDK] nacl_io: remove getcwd() implemenation (rely on glibc/newlib versions)

[NaCl SDK] nacl_io: remove getcwd() implemenation (rely on glibc/newlib versions)

Previsouly we didn't have a working version of getcwd()
in newlib (libnacl) but we do now.

Secondly the resean for intercepting getcwd() directly
was due to gtest calling this in a static constructor.
gtest was recently changed to handle the failure of
getcwd() under NaCl so this workaround is no longer
needed.

BUG=437075
Committed: https://crrev.com/cd49bee13b46af6a4768836b8f89707d0e15f1f6
Cr-Commit-Position: refs/heads/master@{#306220}

[Sam Clegg, 2014-11-30 17:05:59]

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

[binji, 2014-12-01 18:51:33]

lgtm

[Sam Clegg, 2014-12-01 18:58:07]

The CQ bit was checked by sbc@chromium.org

[commit-bot: I haz the power, 2014-12-01 18:59:56]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/756333005/1

[commit-bot: I haz the power, 2014-12-01 19:02:21]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2014-12-01 19:03:28]

Patchset 1 (id:??) landed as
https://crrev.com/cd49bee13b46af6a4768836b8f89707d0e15f1f6
Cr-Commit-Position: refs/heads/master@{#306220}