The test for this is artificial as I'm not aware of any upstream targets
that use DW_CFA_val_offset
RegisterContextUnwind::ReadFrameAddress now reports how it's attempting
to obtain the CFA unless all success/failure cases emit logs that
clearly identify the method it was attempting. Previously several of the
existing failure paths emit no message or a message that's
indistinguishable from those on other paths.
c455c4e2d7