[libbacktrace] Fix memory leak in build_address_map

[libbacktrace] Fix memory leak in build_address_map

While upon failure in build_address_map we call free_unit_addrs_vector, this
does not actually free the addrs vector, but merely the abbrevs of the units
pointed at by the elements of the addrs vector.

Fix this by adding code to build_address_map to make sure that the addrs vector
is freed upon failure.

Bootstrapped and reg-tested on x86_64.

2018-12-28  Tom de Vries  <tdevries@suse.de>

	* dwarf.c (build_address_map): Free addrs vector upon failure.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@267442 138bc75d-0d04-0410-961f-82ee72b054a4