[binutils-gdb] Set TYPE_LENGTH on a variant part

[sergiodj+buildbot at sergiodj dot net]

*** TEST RESULTS FOR COMMIT c8c81635739435a31860ff5f1e49743d80321f43 ***

Author: Tom Tromey <tom@tromey.com>
Branch: master
Commit: c8c81635739435a31860ff5f1e49743d80321f43

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.

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

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