x/vuln: add support for stripped darwin binaries

[zpavlinovic]

The full support for stripping darwin binaries is expected in Go 1.22. When this happens, add support for analyzing stripped darwin binaries.

CL to track: https://go-review.googlesource.com/c/go/+/492744

[gopherbot]

Change https://go.dev/cl/522157 mentions this issue: internal/vulncheck/internal/buildinfo: support stripped darwin binaries