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 builds.

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.

BUG=302040, 341805
TBR=thakis@chromium.org,mseaborn@chromium.org

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=263625

[Alexander Potapenko, 2014-04-14 11:08:10]

Nico, Mark: TBR (you've reviewed this CL once or twice already)

[Alexander Potapenko, 2014-04-14 11:08:17]

The CQ bit was checked by glider@chromium.org

[commit-bot: I haz the power, 2014-04-14 11:08:28]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/glider@chromium.org/230263003/40001

[commit-bot: I haz the power, 2014-04-14 13:56:37]

Change committed as 263625