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/1179393004/

TBR=thakis@chromium.org

Committed: https://crrev.com/07d847b1c5451748f16f4e7973ce8ef9078d47a2
Cr-Commit-Position: refs/heads/master@{#334690}

[brettw, 2015-06-16 16:36:27]

The CQ bit was checked by brettw@chromium.org

[brettw, 2015-06-16 16:36:52]

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

[commit-bot: I haz the power, 2015-06-16 16:37:07]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1182663007/20001

[Nico, 2015-06-16 16:38:02]

lgtm

[commit-bot: I haz the power, 2015-06-16 18:07:38]

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

[commit-bot: I haz the power, 2015-06-16 18:07:40]

Try jobs failed on following builders:
  win_chromium_rel_ng on tryserver.chromium.win (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.win/builders/win_chromium_rel_...)

[brettw, 2015-06-16 20:08:10]

The CQ bit was checked by brettw@chromium.org

[commit-bot: I haz the power, 2015-06-16 20:11:28]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1182663007/20001

[commit-bot: I haz the power, 2015-06-16 20:59:12]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-06-16 21:00:10]

Patchset 2 (id:??) landed as
https://crrev.com/07d847b1c5451748f16f4e7973ce8ef9078d47a2
Cr-Commit-Position: refs/heads/master@{#334690}

[brettw, 2015-06-16 23:28:45]

A revert of this CL (patchset #2 id:20001) has been created in
https://codereview.chromium.org/1187233002/ by brettw@chromium.org.

The reason for reverting is: Broke Linux clobber:

https://build.chromium.org/p/chromium.linux/builders/Linux%20GN%20Clobber/bui....