Fix some build symbol configuration.

Fix some build symbol configuration.

Remove -gdwarf-4 from GYP build. This is the default for GCC 4.8 which is now required, so this command-line argument is redundant.

Only set use_debug_fission in the GN build in debug mode. This matches GYP. Release mode symbols will be non-fission.

Implement linux_symbols target in GN. Convert dump_app_syms from sh to Python for better GN usability, and it's more readable for normal programmers on the team.

Reland of https://codereview.chromium.org/1182663007/
Reland of https://codereview.chromium.org/1179393004/
TBR=thakis@chromium.org

Committed: https://crrev.com/2f27f9bf85b21f149c5972197ef07f957fe20b41
Cr-Commit-Position: refs/heads/master@{#335370}

[brettw, 2015-06-19 17:17:17]

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

[commit-bot: I haz the power, 2015-06-19 17:19:11]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1197793002/20001

[brettw, 2015-06-19 17:21:56]

I'm guessing the problem is a path issue.

[commit-bot: I haz the power, 2015-06-19 19:34:40]

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

[commit-bot: I haz the power, 2015-06-19 19:34:40]

Dry run: Try jobs failed on following builders:
  linux_android_rel_ng on tryserver.chromium.linux (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/linux_android_r...)

[brettw, 2015-06-19 21:04:55]

The CQ bit was checked by brettw@chromium.org

[commit-bot: I haz the power, 2015-06-19 21:06:18]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1197793002/20001

[commit-bot: I haz the power, 2015-06-19 22:35:14]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-06-19 22:37:22]

Patchset 2 (id:??) landed as
https://crrev.com/2f27f9bf85b21f149c5972197ef07f957fe20b41
Cr-Commit-Position: refs/heads/master@{#335370}