Mark discriminants as artificial in gdb.dwarf2/variant.exp
While working on a variant part patch, I notcied that
gdb.dwarf2/variant.exp does not mark the discriminant members as
DW_AT_artificial. However, it should, as this is what the real Rust
compiler does, and how the Rust language support is supposed to work.
gdb/testsuite/ChangeLog
2020-03-11 Tom Tromey <tromey@adacore.com>
* gdb.dwarf2/variant.exp: Mark discriminants as artificial.