fix: node s2i build when node_modules present

This is workaround for two bug in another components:
* The s2i CLI/library is not honoring the `--exclude` flag when used with
  the `--as-dockerfile` flag.
* The node s2i image is not working if project contains `node_modules`
  directory with NodeJS modules.

If only one of the bugs above were fixed this commit wouldn't be
necessary.

Signed-off-by: Matej Vasek <mvasek@redhat.com>

pkg/builders/s2i/builder.go

@@ -10,6 +10,7 @@ import (
 	"net/url"
 	"os"
 	"path/filepath"
+	"regexp"
 	"strings"
 
 	"github.com/docker/docker/api/types"
@@ -204,6 +205,9 @@ func (b *Builder) Build(ctx context.Context, f fn.Function) (err error) {
 
 	pr, pw := io.Pipe()
 
+	// s2i apparently is not excluding the files in --as-dockerfile mode
+	exclude := regexp.MustCompile(cfg.ExcludeRegExp)
+
 	const up = ".." + string(os.PathSeparator)
 	go func() {
 		tw := tar.NewWriter(pw)
@@ -220,6 +224,10 @@ func (b *Builder) Build(ctx context.Context, f fn.Function) (err error) {
 				return nil
 			}
 
+			if exclude.MatchString(p) {
+				return nil
+			}
+
 			lnk := ""
 			if fi.Mode()&fs.ModeSymlink != 0 {
 				lnk, err = os.Readlink(path)