cmd/go: +dirty in version stamping doesn't combine well with +incompatible [1.24 backport]

[gopherbot]

@xnox requested issue #71971 to be considered for backport to the next 1.24 minor release.

@gopherbot please backport to Go 1.24. This bug is producing unparsable buildinfo for compliant validators.

[gopherbot]

Change https://go.dev/cl/668135 mentions this issue: [release-branch.go1.24] cmd/go/internal/load: join incompatible and dirty build specifiers with .

[gopherbot]

Closed by merging CL 668135 (commit c1f9c2c) to release-branch.go1.24.