quota: add build tag to disable it

change backported from Moby.

Signed-off-by: Giuseppe Scrivano <gscrivan@redhat.com>

drivers/quota/projectquota.go

@@ -1,4 +1,4 @@
-// +build linux
+// +build linux,!exclude_disk_quota
 
 //
 // projectquota.go - implements XFS project quota controls

drivers/quota/projectquota_unsupported.go

@@ -0,0 +1,36 @@
+// +build linux,exclude_disk_quota
+
+package quota
+
+import (
+	"github.com/pkg/errors"
+)
+
+// Quota limit params - currently we only control blocks hard limit
+type Quota struct {
+        Size uint64
+}
+
+// Control - Context to be used by storage driver (e.g. overlay)
+// who wants to apply project quotas to container dirs
+type Control struct {
+}
+
+var (
+	errQuotaNotSupported = errors.New("filesystem does not support, or has not enabled quotas")
+)
+
+func NewControl(basePath string) (*Control, error) {
+	return nil, errQuotaNotSupported
+}
+
+// SetQuota - assign a unique project id to directory and set the quota limits
+// for that project id
+func (q *Control) SetQuota(targetPath string, quota Quota) error {
+	return errQuotaNotSupported
+}
+
+// GetQuota - get the quota limits of a directory that was configured with SetQuota
+func (q *Control) GetQuota(targetPath string, quota *Quota) error {
+	return errQuotaNotSupported
+}