Don't share the options map

Without this I get an exception when building multiple images in a
compose run.

```
fatal error: concurrent map writes

goroutine 16 [running]:
github.com/docker/compose/v2/pkg/compose.(*composeService).build.func1({0x2cba4e0, 0xc00019b2c0}, {0xc000233150?, 0xd?})
        github.com/docker/compose/v2/pkg/compose/build.go:95 +0x652
github.com/docker/compose/v2/pkg/compose.(*graphTraversal).run.func1()
        github.com/docker/compose/v2/pkg/compose/dependencies.go:127 +0x63
golang.org/x/sync/errgroup.(*Group).Go.func1()
        golang.org/x/sync@v0.1.0/errgroup/errgroup.go:75 +0x64
created by golang.org/x/sync/errgroup.(*Group).Go
        golang.org/x/sync@v0.1.0/errgroup/errgroup.go:72 +0xa5
...
```

I'm not sure why the map is currently shared, but with this patch
applied my docker-compose build run works.

Signed-off-by: Edward Muller <emuller@fastly.com>

pkg/compose/build.go

@@ -48,7 +48,6 @@ func (s *composeService) Build(ctx context.Context, project *types.Project, opti
 }
 
 func (s *composeService) build(ctx context.Context, project *types.Project, options api.BuildOptions) error {
-	opts := map[string]build.Options{}
 	args := flatten(options.Args.Resolve(envResolver(project.Environment)))
 
 	return InDependencyOrder(ctx, project, func(ctx context.Context, name string) error {
@@ -92,7 +91,7 @@ func (s *composeService) build(ctx context.Context, project *types.Project, opti
 				Attrs: map[string]string{},
 			}}
 		}
-		opts[imageName] = buildOptions
+		opts := map[string]build.Options{imageName: buildOptions}
 		_, err = s.doBuild(ctx, project, opts, options.Progress)
 		return err
 	}, func(traversal *graphTraversal) {