Update buildah to current master

Vendor some changes to parsing code that we need for Podman.

Signed-off-by: Matthew Heon <matthew.heon@pm.me>

vendor/github.com/containers/buildah/util/util_unix.go

@@ -0,0 +1,31 @@
+// +build linux darwin
+
+package util
+
+import (
+	"os"
+	"sync"
+	"syscall"
+)
+
+type hardlinkDeviceAndInode struct {
+	device, inode uint64
+}
+
+type HardlinkChecker struct {
+	hardlinks sync.Map
+}
+
+func (h *HardlinkChecker) Check(fi os.FileInfo) string {
+	if st, ok := fi.Sys().(*syscall.Stat_t); ok && fi.Mode().IsRegular() && st.Nlink > 1 {
+		if name, ok := h.hardlinks.Load(makeHardlinkDeviceAndInode(st)); ok && name.(string) != "" {
+			return name.(string)
+		}
+	}
+	return ""
+}
+func (h *HardlinkChecker) Add(fi os.FileInfo, name string) {
+	if st, ok := fi.Sys().(*syscall.Stat_t); ok && fi.Mode().IsRegular() && st.Nlink > 1 {
+		h.hardlinks.Store(makeHardlinkDeviceAndInode(st), name)
+	}
+}