Bump github.com/containers/buildah from 1.8.4 to 1.11.4

Bumps [github.com/containers/buildah](https://github.com/containers/buildah) from 1.8.4 to 1.11.4.
- [Release notes](https://github.com/containers/buildah/releases)
- [Changelog](https://github.com/containers/buildah/blob/master/CHANGELOG.md)
- [Commits](https://github.com/containers/buildah/compare/v1.8.4...v1.11.4)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>
Signed-off-by: Valentin Rothberg <rothberg@redhat.com>

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

@@ -0,0 +1,43 @@
+// Copyright 2019 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 (
+	"io/ioutil"
+	"os"
+	"strings"
+)
+
+// Environ reads process environments from /proc/<pid>/environ
+func (p Proc) Environ() ([]string, error) {
+	environments := make([]string, 0)
+
+	f, err := os.Open(p.path("environ"))
+	if err != nil {
+		return environments, err
+	}
+	defer f.Close()
+
+	data, err := ioutil.ReadAll(f)
+	if err != nil {
+		return environments, err
+	}
+
+	environments = strings.Split(string(data), "\000")
+	if len(environments) > 0 {
+		environments = environments[:len(environments)-1]
+	}
+
+	return environments, nil
+}