[lldb][test] Disable TestSBValueUnsignedEnumBitField.py for old DWARF versions

[Michael137]

Summary

With older DWARF versions we don't encode the enum's underlying
type in DWARF. In those cases LLDB sign-extends the bitfield as
a signed integer. Without the actual enum type being present in
DWARF there's not much we can do.

[fdeazeve]

LGTM!

[Michael137]

• Works on DWARFv3

lldb/test/API/python_api/sbvalue_unsigned_enum_bitfield_value/TestSBValueUnsignedEnumBitField.py

 """
 Test that SBValue doesn't incorrectly sign-extend
 the Scalar value of a bitfield that has an unsigned
 enum type.
 
 We test this by assigning to a bit-field a value
 that is out-of-range of it's signed counterpart.
 I.e., with a bit-field of width 4, assigning
 8 to it would be out-of-range if we treated it
 as a signed. If LLDB were to sign-extend the Scalar
 (which shouldn't happen for unsigned bit-fields)
 it would left-fill the result with 1s; we test
 for this not to happen.
 """
 
 import lldbsuite.test.lldbinline as lldbinline
+from lldbsuite.test.decorators import *
 
-lldbinline.MakeInlineTest(__file__, globals())
+lldbinline.MakeInlineTest(__file__, globals(),
+                          [skipIf(dwarf_version=['<', '3'])])