Update module github.com/openshift/imagebuilder to v1.2.15

Signed-off-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

vendor/github.com/openshift/imagebuilder/internal/env.go

@@ -0,0 +1,23 @@
+package internal
+
+import "strings"
+
+type EnvironmentSlice []string
+
+func (e EnvironmentSlice) Keys() []string {
+	keys := make([]string, 0, len(e))
+	for _, kv := range e {
+		k, _, _ := strings.Cut(kv, "=")
+		keys = append(keys, k)
+	}
+	return keys
+}
+
+func (e EnvironmentSlice) Get(key string) (string, bool) {
+	for _, kv := range e {
+		if k, v, ok := strings.Cut(kv, "="); ok && k == key {
+			return v, true
+		}
+	}
+	return "", false
+}