Set package configuration options

Set package configuration options

Forwarded: not-needed

Configure Abseil for Debian.

  - Set the SONAME appropriately.

  - To minimize the possibility of future ABI breakage, treat absl::any,
    absl::optional, absl::string_view, and absl::variant as their own types
    (rather than aliases for the std:: versions), and compile everything in an
    inline namespace.

  - Enable upstream's hardened build mode.

  - Disable Intel SSE2 on i386, since Debian supports some i386 processors
    without that extension. Keep it enabled on amd64, since all amd64 processors
    have it.

  - Disable Intel SSSE3 entirely, since no i386 processor supports it and Debian
    supports amd64 processors without it.

Gbp-Pq: Name configure.diff