[patch][gold] Fix pr18327

[Cary Coutant]

> 2015-04-27  Rafael Ávila de Espíndola <rafael.espindola@gmail.com>
>
> * output.cc (Output_section::is_input_address_mapped): Assume a missing
> entry is mapped.
> * Makefile.am: Add the eh_test test.
> * Makefile.in: Regenerate.

You forgot to add the new source files.

-cary