Add cap-add and cap-drop to build man page

Signed-off-by: TomSweeneyRedHat <tsweeney@redhat.com>

Closes: #968
Approved by: mheon

vendor/github.com/projectatomic/buildah/bind/mount_unsupported.go

@@ -0,0 +1,25 @@
+// +build !linux
+
+package bind
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+	"sort"
+	"strings"
+	"syscall"
+
+	"github.com/containers/storage/pkg/idtools"
+	"github.com/containers/storage/pkg/mount"
+	"github.com/opencontainers/runtime-spec/specs-go"
+	"github.com/pkg/errors"
+	"github.com/sirupsen/logrus"
+	"golang.org/x/sys/unix"
+)
+
+// SetupIntermediateMountNamespace returns a no-op unmountAll() and no error.
+func SetupIntermediateMountNamespace(spec *specs.Spec, bundlePath string) (unmountAll func() error, err error) {
+	stripNoBuildahBindOption(spec)
+	return func() error { return nil }, nil
+}