Make Windows build skip BlockMode code.

PVC block mode backup and restore introduced some OS specific
system calls. Those calls are not available for Windows, so
add both non Windows version and Windows version code, and
return error for block mode on the Windows platform.

Signed-off-by: Xun Jiang <jxun@vmware.com>

changelogs/unreleased/6986-blackpiglet

@@ -0,0 +1 @@
+Add both non-Windows version and Windows version code for PVC block mode logic.

pkg/uploader/kopia/block_backup.go

@@ -1,3 +1,6 @@
+//go:build !windows
+// +build !windows
+
 /*
 Copyright The Velero Contributors.
 

pkg/uploader/kopia/block_backup_windows.go

@@ -0,0 +1,30 @@
+//go:build windows
+// +build windows
+
+/*
+Copyright The Velero Contributors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package kopia
+
+import (
+	"fmt"
+
+	"github.com/kopia/kopia/fs"
+)
+
+func getLocalBlockEntry(sourcePath string) (fs.Entry, error) {
+	return nil, fmt.Errorf("block mode is not supported for Windows")
+}

pkg/uploader/kopia/block_restore.go

@@ -1,3 +1,6 @@
+//go:build !windows
+// +build !windows
+
 /*
 Copyright The Velero Contributors.
 

pkg/uploader/kopia/block_restore_windows.go

@@ -0,0 +1,42 @@
+//go:build windows
+// +build windows
+
+/*
+Copyright The Velero Contributors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package kopia
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/kopia/kopia/fs"
+	"github.com/kopia/kopia/snapshot/restore"
+)
+
+type BlockOutput struct {
+	*restore.FilesystemOutput
+
+	targetFileName string
+}
+
+func (o *BlockOutput) WriteFile(ctx context.Context, relativePath string, remoteFile fs.File) error {
+	return fmt.Errorf("block mode is not supported for Windows")
+}
+
+func (o *BlockOutput) BeginDirectory(ctx context.Context, relativePath string, e fs.Directory) error {
+	return fmt.Errorf("block mode is not supported for Windows")
+}