Roll buildtools to 15f5fc to roll GN to 326666:327383

Roll buildtools to 15f5fc to roll GN 326666:327383

Roll GN 326666:327383

This includes the following fixes:
- "gn help grammar" is included in "gn help all"
- phony rules for executables will be correctly
  generated (previously we would not generate a
  rule for the unit_tests executable because
  there were other targets with the 'unit_tests'
  name)
- paths can be resolved in the GN args file

R=brettw@chromium.org
BUG=

Committed: https://crrev.com/a272915c9fb33c1b1bd408330bba6889499f09bc
Cr-Commit-Position: refs/heads/master@{#327491}

[Dirk Pranke, 2015-04-29 02:13:12]

dpranke@chromium.org changed reviewers:
+ brettw@chromium.org

[Dirk Pranke, 2015-04-29 02:13:18]

The CQ bit was checked by dpranke@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2015-04-29 02:14:59]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1111953004/20001

[brettw, 2015-04-29 04:33:51]

lgtm

[commit-bot: I haz the power, 2015-04-29 06:18:19]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-04-29 06:18:20]

Dry run: Try jobs failed on following builders:
  chromium_presubmit on tryserver.chromium.linux (JOB_TIMED_OUT, no build URL)

[Dirk Pranke, 2015-04-29 15:25:50]

The CQ bit was checked by dpranke@chromium.org

[commit-bot: I haz the power, 2015-04-29 15:26:10]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1111953004/20001

[commit-bot: I haz the power, 2015-04-29 15:27:05]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-04-29 15:27:58]

Patchset 2 (id:??) landed as
https://crrev.com/a272915c9fb33c1b1bd408330bba6889499f09bc
Cr-Commit-Position: refs/heads/master@{#327491}