Add a PT_NOTE section to mark build_id.

Adding a PT_NOTE section to mark the location of the build_id note will allow
us to extract it from dl_iterate_phdrs at runtime.
This in turn will facilitate providing module information with minidumps.

BUG=https://code.google.com/p/nativeclient/issues/detail?id=3607
TEST=None
R=mcgrathr@chromium.org, mseaborn@chromium.org

Review URL: https://codereview.chromium.org/21636003
7 files changed