Unbreak the debuginfo tests.

The variant used in debug-info/method-on-enum.rs had its layout changed
by the smaller discriminant, so that the `u32` no longer overlaps both
of the `u16`s, and thus the debugger is printing partially uninitialized
data when it prints the wrong variant.

Thus, the test runner is modified to accept wildcards (using a string
that should be unlikely to occur literally), to allow for this.