fix(go-licences): fix running on macOS when Go is upgraded

Running go-licenses breaks after upgrading Go through Homebrew, as the
GOROOT path on the machine no longer matches the one used to build
go-licenses.

As a workaround, explicitly set GOROOT.

See google/go-licenses#149 for reference.

tools/sggolicenses/tools.go

@@ -8,6 +8,7 @@ import (
 	"io/fs"
 	"os/exec"
 	"path/filepath"
+	"runtime"
 	"strings"
 
 	"go.einride.tech/sage/sg"
@@ -55,6 +56,17 @@ func Check(ctx context.Context, disallowedTypes ...string) error {
 		}
 		cmd := Command(ctx, args...)
 		cmd.Dir = filepath.Dir(path)
+		// go-licenses tries to exclude standard library packages by checking if they are prefixed
+		// with `runtime.GOROOT()`. However, if the tool is not run with a GOROOT environment variable,
+		// this will return the GOROOT path used during build time. This typically works on Linux, but on macOS
+		// with Homebrew, the GOROOT is version prefixed, which breaks as soon as Go is upgraded.
+		// For example: /opt/homebrew/Cellar/go/1.19.4/libexec
+		//
+		// As a workaround, add the GOROOT environment variable to the result of `runtime.GOROOT()` called here.
+		// This should work as the Sage binary is built on the same machine that executes it.
+		// See: https://github.com/google/go-licenses/issues/149
+		cmd.Env = append(cmd.Env, fmt.Sprintf("GOROOT=%s", runtime.GOROOT()))
+
 		commands = append(commands, cmd)
 		return cmd.Start()
 	}); err != nil {