[debuginfo] Fix and unify handling of fat pointers in debuginfo: Don't mark fat pointer fields as artificial.

LLDB does not seem to see fields if they are marked with DW_AT_artificial
which breaks pretty printers that use these fields for decoding fat pointers.

Author: michaelwoerister

compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs

@@ -491,7 +491,7 @@ fn pointer_or_reference_metadata<'ll, 'tcx>(
                     offset: layout.fields.offset(abi::FAT_PTR_ADDR),
                     size: addr_field.size,
                     align: addr_field.align.abi,
-                    flags: DIFlags::FlagArtificial,
+                    flags: DIFlags::FlagZero,
                     discriminant: None,
                     source_info: None,
                 },
@@ -501,7 +501,7 @@ fn pointer_or_reference_metadata<'ll, 'tcx>(
                     offset: layout.fields.offset(abi::FAT_PTR_EXTRA),
                     size: extra_field.size,
                     align: extra_field.align.abi,
-                    flags: DIFlags::FlagArtificial,
+                    flags: DIFlags::FlagZero,
                     discriminant: None,
                     source_info: None,
                 },