Fix goreleaser archive format

Use the binary name, not the project name, as the first part of the
artifact. This prevents us from accidentally releasing `base-image` as
`cog`, for example.

As some braces to go with my belt, restrict our archive to only include
the cog binary for now.

.goreleaser.yaml

@@ -31,8 +31,10 @@ builds:
       - "-s -w -X github.com/replicate/cog/pkg/global.Version={{.Version}} -X github.com/replicate/cog/pkg/global.Commit={{.Commit}} -X github.com/replicate/cog/pkg/global.BuildTime={{.Date}}"
 archives:
   - format: binary
+    builds:
+      - cog # for now we only release cog
     name_template: >-
-      {{ .ProjectName }}_
+      {{ .Binary }}_
       {{- title .Os }}_
       {{- if eq .Arch "amd64" }}x86_64
       {{- else if eq .Arch "386" }}i386