Fix soong_zip printing warnings with --ignore_missing_files

We weren't defaulting args.Stderr to os.Stderr, so we had been calling
fmt.Fprintln with `nil`.

Test: soong_zip --ignore_missing_files -C test/ -f abc -o test.zip
Change-Id: I0421f4bfb07fa36edf86c68ffc847995777c8221

1 files changed, 3 insertions, 3 deletions

diff --git a/zip/zip.go b/zip/zip.go
index 774966a7..1f5fe433 100644
--- a/zip/zip.go
+++ b/zip/zip.go
@@ -317,7 +317,7 @@ func ZipTo(args ZipArgs, w io.Writer) error {
 					Err:  os.ErrNotExist,
 				}
 				if args.IgnoreMissingFiles {
-					fmt.Fprintln(args.Stderr, "warning:", err)
+					fmt.Fprintln(z.stderr, "warning:", err)
 				} else {
 					return err
 				}
@@ -334,7 +334,7 @@ func ZipTo(args ZipArgs, w io.Writer) error {
 					Err:  os.ErrNotExist,
 				}
 				if args.IgnoreMissingFiles {
-					fmt.Fprintln(args.Stderr, "warning:", err)
+					fmt.Fprintln(z.stderr, "warning:", err)
 				} else {
 					return err
 				}
@@ -345,7 +345,7 @@ func ZipTo(args ZipArgs, w io.Writer) error {
 					Err:  syscall.ENOTDIR,
 				}
 				if args.IgnoreMissingFiles {
-					fmt.Fprintln(args.Stderr, "warning:", err)
+					fmt.Fprintln(z.stderr, "warning:", err)
 				} else {
 					return err
 				}