chore: switch release pipeline

fix: set osxcross CC for darwin cross-compile in goreleaser

Darwin builds were inheriting the goreleaser-cross container's default
linux gcc, which rejects clang's -arch flag. Point CC at o64-clang /
oa64-clang so CGO picks up the osxcross toolchain.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>