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

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.

GYP changes for OSX and iOS will be committed separately.

BUG=302040
R=thakis@chromium.org

Review URL: https://codereview.chromium.org/25687005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@234207 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 234207