This patch renames build_id_find_nhdr() to
build_id_find_nhdr_for_addr(), and changes it to never examine the
library name.

Tested on Fedora by confirming that build_id_get_data() returns the same
build-id as the file(1) tool. For BSD, I confirmed that the API used
(dladdr() and struct Dl_info) is documented in FreeBSD's manpages.

This solves two problems:

    - We can now the query the build-id without knowing the installed library's
      filename.

      This matters because Android requires specific filenames for HAL
      modules, such as "/vendor/lib/hw/vulkan.${board}.so". The HAL
      filenames do not follow the Unix convention of "libfoo.so".  In
      other words, the same query code will now work on Linux and Android.

    - Querying the build-id now works correctly when the process
      contains multiple shared objects with the same basename.
      (Admittedly, this is a highly unlikely scenario).

Cc: Jonathan Gray <jsg@jsg.id.au>
Reviewed-by: Matt Turner <mattst88@gmail.com>
Reviewed-by: Emil Velikov <emil.velikov@collabora.com>