[PATCH v2] gold: add --package-metadata

[Cary Coutant]

> v2: apply fixes from review
>
>  elfcpp/elfcpp.h                        |  4 ++-
>  gold/Makefile.am                       |  8 ++---
>  gold/configure.ac                      | 26 ++++++++++++++
>  gold/layout.cc                         | 50 ++++++++++++++++++++++++++
>  gold/layout.h                          |  6 ++++
>  gold/options.h                         |  4 +++
>  gold/testsuite/Makefile.am             | 15 +++++---
>  gold/testsuite/package_metadata_main.c |  5 +++

Committed. Thanks!

elfcpp/
        * elfcpp.h: Add FDO_PACKAGING_METADATA note type.

gold/
        * Makefile.am: Add jansson flags and libraries.
        * configure.ac: Check for jansson library.
        * layout.cc (Layout::create_notes): Call create_package_metadata().
        (Layout::create_package_metadata): New function.
        * layout.h (Layout::create_package_metadata): New function.
        (Layout::package_metadata_note_): New data member.
        * options.h (class General_options): Add --package-metadata option.
        * testsuite/Makefile.am (object_unittest): Add jansson libraries.
        (binary_unittest): Likewise.
        (leb128_unittest): Likewise.
        (overflow_unittest): Likewise.
        (package_metadata_test): New test.
        * testsuite/package_metadata_main.c: New test source.

-cary