Add containers-common spec and command to podman

Since containers-common package is tied to specific versions
of Podman, add tools to build the package into the contrib directory
This should help other distributions to figure out which commont
package to ship.

Signed-off-by: Daniel J Walsh <dwalsh@redhat.com>

vendor/github.com/prometheus/procfs/cmdline.go

@@ -0,0 +1,30 @@
+// Copyright 2021 The Prometheus 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.
+
+package procfs
+
+import (
+	"strings"
+
+	"github.com/prometheus/procfs/internal/util"
+)
+
+// CmdLine returns the command line of the kernel.
+func (fs FS) CmdLine() ([]string, error) {
+	data, err := util.ReadFileNoStat(fs.proc.Path("cmdline"))
+	if err != nil {
+		return nil, err
+	}
+
+	return strings.Fields(string(data)), nil
+}