Require build directories exist for some GN commands.

Require build directories exist for some GN commands.

Some GN commands just query the state of the build. They generally take the
build directory as a first argument. But this is easy to forget and GN will
auto-create these directories if they don't exist. So I end up with directories
named "base/*" because I was trying to list all targets in base but forgot the
build argument.

This patch requires that the build directory contain a build.ninja file for
the "querying" commands to prevent this case.

Committed: https://crrev.com/4dd3ef06036b5b7bfc430ee4a5013856cfe8d872
Cr-Commit-Position: refs/heads/master@{#294071}

[brettw, 2014-09-09 20:24:23]

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

[jamesr, 2014-09-09 20:46:50]

lgtm. i've had the same thing

[brettw, 2014-09-09 20:54:04]

The CQ bit was checked by brettw@chromium.org

[commit-bot: I haz the power, 2014-09-09 20:58:27]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/brettw@chromium.org/558763002/1

[commit-bot: I haz the power, 2014-09-09 22:05:58]

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

[commit-bot: I haz the power, 2014-09-09 22:05:59]

Try jobs failed on following builders:
  win8_chromium_rel on tryserver.chromium.win
(http://build.chromium.org/p/tryserver.chromium.win/builders/win8_chromium_rel...)
  win_chromium_compile_dbg on tryserver.chromium.win
(http://build.chromium.org/p/tryserver.chromium.win/builders/win_chromium_comp...)
  win_chromium_rel_swarming on tryserver.chromium.win
(http://build.chromium.org/p/tryserver.chromium.win/builders/win_chromium_rel_...)
  win_chromium_x64_rel_swarming on tryserver.chromium.win
(http://build.chromium.org/p/tryserver.chromium.win/builders/win_chromium_x64_...)

[brettw, 2014-09-09 23:20:05]

The CQ bit was checked by brettw@chromium.org

[commit-bot: I haz the power, 2014-09-09 23:25:08]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/brettw@chromium.org/558763002/20001

[commit-bot: I haz the power, 2014-09-10 01:46:54]

Committed patchset #2 (id:20001) as 049db789e25edf2f4a23f43d9f7d9018db0602a2

[commit-bot: I haz the power, 2014-09-10 03:57:35]

Patchset 2 (id:??) landed as
https://crrev.com/4dd3ef06036b5b7bfc430ee4a5013856cfe8d872
Cr-Commit-Position: refs/heads/master@{#294071}