Add cross-compiling for freebsd

magefile.go

@@ -467,6 +467,7 @@ func (Release) Release(ctx context.Context) error {
 	errs.Go((Release{}).Windows)
 	errs.Go((Release{}).Linux)
 	errs.Go((Release{}).Darwin)
+	errs.Go((Release{}).FreeBSD)
 	if err := errs.Wait(); err != nil {
 		return err
 	}
@@ -510,6 +511,9 @@ func runXgo(targets string) error {
 	if strings.HasPrefix(targets, "darwin") {
 		extraLdflags = ""
 	}
+	if strings.HasPrefix(targets, "freebsd") {
+		extraLdflags = ""
+	}
 
 	runAndStreamOutput("xgo",
 		"-dest", RootPath+"/"+DIST+"/binaries",
@@ -546,6 +550,11 @@ func (Release) Darwin() error {
 	return runXgo("darwin-10.15/*")
 }
 
+// Builds binaries for freebsd
+func (Release) FreeBSD() error {
+	return runXgo("freebsd/amd64")
+}
+
 func (Release) Xgo(target string) error {
 	parts := strings.Split(target, "/")
 	if len(parts) < 2 {