dashboard: add freebsd-[amd64|386]-13_0 builders

This change adds builders for FreeBSD 13.0.

Updates golang/go#46272
Fixes golang/go#45903

Change-Id: I92f68f8d5eeee2d3bae8864dbfe5ee61b93ea677
Reviewed-on: https://go-review.googlesource.com/c/build/+/365314
Trust: Carlos Amedee <carlos@golang.org>
Run-TryBot: Carlos Amedee <carlos@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>
diff --git a/dashboard/builders_test.go b/dashboard/builders_test.go
index 7e7e023..cd97cd0 100644
--- a/dashboard/builders_test.go
+++ b/dashboard/builders_test.go
@@ -240,8 +240,10 @@
 			want: []string{
 				"android-amd64-emu",
 				"freebsd-386-11_4",
+				"freebsd-386-13_0",
 				"freebsd-amd64-11_4",
 				"freebsd-amd64-12_2",
+				"freebsd-amd64-13_0",
 				"linux-386",
 				"linux-amd64",
 				"linux-amd64-race",
@@ -429,6 +431,14 @@
 		{b("openbsd-amd64-68@go1.15", "go"), both},
 		{b("openbsd-amd64-68@go1.14", "go"), both},
 
+		// FreeBSD 13.0
+		{b("freebsd-amd64-13_0", "go"), onlyPost},
+		{b("freebsd-amd64-13_0", "net"), onlyPost},
+		{b("freebsd-amd64-13_0", "mobile"), none},
+		{b("freebsd-386-13_0", "go"), onlyPost},
+		{b("freebsd-386-13_0", "net"), onlyPost},
+		{b("freebsd-386-13_0", "mobile"), none},
+
 		// FreeBSD 12.2
 		{b("freebsd-amd64-12_2", "go"), both},
 		{b("freebsd-amd64-12_2", "net"), both},