osbuildexecutor: allow file type tar.TypeGNUSparse too

We need to allow files of type `tar.TypeGNUSparse` in the result
that we get from the osbuild-worker-executor too.

internal/osbuildexecutor/runner-impl-aws-ec2.go

@@ -210,7 +210,7 @@ func validateOutputArchive(outputTarPath string) error {
 		}
 		// protect against someone smuggling in eg. device files
 		// XXX: should we support symlinks here?
-		if !slices.Contains([]byte{tar.TypeReg, tar.TypeDir}, hdr.Typeflag) {
+		if !slices.Contains([]byte{tar.TypeReg, tar.TypeDir, tar.TypeGNUSparse}, hdr.Typeflag) {
 			return fmt.Errorf("name %q must be a file/dir, is header type %q", hdr.Name, hdr.Typeflag)
 		}
 		// protect against executables, this implicitly protects

internal/osbuildexecutor/runner-impl-aws-ec2_test.go

@@ -160,11 +160,35 @@ func TestValidateOutputArchiveHappy(t *testing.T) {
 	testTarPath := makeTestTarfile(t, map[*tar.Header]string{
 		&tar.Header{Name: "file1"}:        "some content",
 		&tar.Header{Name: "path/to/file"}: "other content",
+		&tar.Header{
+			Name:     "path/to/dir",
+			Typeflag: tar.TypeDir,
+		}: "",
 	})
 	err := osbuildexecutor.ValidateOutputArchive(testTarPath)
 	assert.NoError(t, err)
 }
 
+func makeSparseFile(t *testing.T, path string) {
+	output, err := exec.Command("truncate", "-s", "10M", path).CombinedOutput()
+	assert.Equal(t, "", string(output))
+	assert.NoError(t, err)
+}
+
+func TestValidateOutputArchiveHappySparseFile(t *testing.T) {
+	// go tar makes support for sparse files very hard, see also
+	// https://github.com/golang/go/issues/22735
+	tmpdir := t.TempDir()
+	makeSparseFile(t, filepath.Join(tmpdir, "big.img"))
+	testTarPath := filepath.Join(t.TempDir(), "test.tar")
+	output, err := exec.Command("tar", "--strip-components=1", "-C", tmpdir, "-c", "-S", "-f", testTarPath, "big.img").CombinedOutput()
+	assert.Equal(t, "", string(output))
+	assert.NoError(t, err)
+
+	err = osbuildexecutor.ValidateOutputArchive(testTarPath)
+	assert.NoError(t, err)
+}
+
 func TestValidateOutputArchiveSadDotDot(t *testing.T) {
 	testTarPath := makeTestTarfile(t, map[*tar.Header]string{
 		&tar.Header{Name: "file1/.."}: "some content",