[NaCl SDK Addin] Fix detection of PNaCl toolchain.

The check was incorrectly looking at the revsion alone which
can be higher for older version (e.g it can be higher on 23
than it is on 24).

BUG=

Review URL: https://codereview.chromium.org/11475048

git-svn-id: https://nativeclient-sdk.googlecode.com/svn/trunk/src@1472 050acbb0-2703-11df-ab0a-9f3f633ae91d
3 files changed