Set the default ASan options for executables built with ASan on Linux.

Set the default ASan options for executables built with ASan on Linux.

This is a copy of https://codereview.chromium.org/201153007 and https://codereview.chromium.org/213113002
updated to the current trunk with more descriptive comments in sanitizer_options.cc and the additional
legacy_pthread_cond=1 option for the Linux Official builds (legacy_pthread_cond is to be deprecated,
thus we don't enable it on the bots).

This CL introduces a module, base/debug/sanitizer_options.cc, which will override
the defaults for various dynamic tools (only ASan at this moment). For every executable
built with a dynamic tool this module will be linked into that executable, providing
weak functions to be called by the tool.

The existing declaration of __asan_default_options() in chrome/app/chrome_exe_main_gtk.cc
has been moved into sanitizer_options.cc (now every binary built with GOOGLE_CHROME_BUILD=1
will have the same options as google-chrome-asan.
The existing declaration of __asan_default_options() in chrome/nacl/nacl_helper_linux.cc
has been kept as is, but we had to remove -Wl,-u_sanitizer_options_link_helper to avoid picking sanitizer_options.cc.

The default options target is deliberately disabled on 32-bit Chromium OS builds,
where one of the host binaries (mksnapshot.ia32) is 32-bit despite host_arch==x86_64.

GYP changes for OSX and iOS will be committed separately.

TBR=thakis@chromium.org,mseaborn@chromium.org
BUG=302040
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=263941

[Alexander Potapenko, 2014-04-15 15:23:50]

TBR
Re-landing this again. Last time the problem was in legacy_pthread_cond=1 flag,
which led to each pthread_cond_init() allocating some memory that was leaked if
the condvar wasn't properly destroyed - this caused LSan reports.
Because the legacy_pthread_cond flag is going to be deprecated, I don't add it
for the developer builds. This flag is however needed to avoid GPU hangs, so I
keep it for the official builds till one or two next Clang releases.

[Alexander Potapenko, 2014-04-15 15:23:58]

The CQ bit was checked by glider@chromium.org

[commit-bot: I haz the power, 2014-04-15 15:24:13]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/glider@chromium.org/238123003/1

[commit-bot: I haz the power, 2014-04-15 15:24:14]

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

[commit-bot: I haz the power, 2014-04-15 15:24:14]

No LGTM from a valid reviewer yet. Only full committers are accepted.
Even if an LGTM may have been provided, it was from a non-committer or
a lowly provisional committer, _not_ a full super star committer.
See http://www.chromium.org/getting-involved/become-a-committer
Note that this has nothing to do with OWNERS files.

[Alexander Potapenko, 2014-04-15 15:26:06]

The CQ bit was checked by glider@chromium.org

[commit-bot: I haz the power, 2014-04-15 15:26:48]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/glider@chromium.org/238123003/1

[commit-bot: I haz the power, 2014-04-15 18:39:24]

Change committed as 263941