[binutils-gdb/gdb-8.2-branch] Set TYPE_LENGTH on a variant part

[sergiodj+buildbot at sergiodj dot net]

*** TEST RESULTS FOR COMMIT c07c917f276d6e055a4e6ba5be5d6b9c4d355de7 ***

Author: Tom Tromey <tom@tromey.com>
Branch: gdb-8.2-branch
Commit: c07c917f276d6e055a4e6ba5be5d6b9c4d355de7

Set TYPE_LENGTH on a variant part

gdb represents a DW_TAG_variant_part as a union.  While normally DWARF
would not set the size of a DW_TAG_variant_part, gdb's representation
requires the TYPE_LENGTH to be set.

This patch arranges to set the TYPE_LENGTH of a variant part if it has
not already been set.

This fixes some Rust regressions when testing against a version of
rustc that emits DW_TAG_variant_part.

2018-08-31  Tom Tromey  <tom@tromey.com>

	* dwarf2read.c (dwarf2_add_field): Set the TYPE_LENGTH of the
	variant part type.