Initial support for zOS

zOS is an IBM Z (mainframe) operating system. In the days of yore, it was MVS.

Signed-off-by: v1gnesh <v1gnesh@users.noreply.github.com>

server/pse/pse_zos.go

@@ -0,0 +1,26 @@
+// Copyright 2022 The NATS Authors
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//go:build zos
+// +build zos
+
+package pse
+
+// This is a placeholder for now.
+func ProcUsage(pcpu *float64, rss, vss *int64) error {
+	*pcpu = 0.0
+	*rss = 0
+	*vss = 0
+
+	return nil
+}

server/sysmem/mem_zos.go

@@ -0,0 +1,22 @@
+// Copyright 2022 The NATS Authors
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//go:build zos
+// +build zos
+
+package sysmem
+
+func Memory() int64 {
+	// TODO: We don't know the system memory
+	return 0
+}