cmd, docker: Updates for infrastructure

These are some changes to the relay pool server, upgrade server, and
crash receiver to run under Kubernetes. It's been in production for a
while.

build.go

@@ -207,6 +207,18 @@ var targets = map[string]target{
 			{src: "AUTHORS", dst: "deb/usr/share/doc/syncthing-relaypoolsrv/AUTHORS.txt", perm: 0644},
 		},
 	},
+	"stupgrades": {
+		name:        "stupgrades",
+		description: "Syncthing Upgrade Check Server",
+		buildPkgs:   []string{"github.com/syncthing/syncthing/cmd/stupgrades"},
+		binaryName:  "stupgrades",
+	},
+	"stcrashreceiver": {
+		name:        "stupgrastcrashreceiverdes",
+		description: "Syncthing Crash Server",
+		buildPkgs:   []string{"github.com/syncthing/syncthing/cmd/stcrashreceiver"},
+		binaryName:  "stcrashreceiver",
+	},
 }
 
 func initTargets() {