Fix "Failed to upload the chunk ... sync ...: operation not supported" issue when using SMB on MacOS. This is done by inspecting the error type and returning the error only if its operation is "sync" and the type is "operation not supported".

Note: this change is my first ever foray into go and based simply on the information provided in: https://forum.duplicacy.com/t/failed-to-upload-the-chunk-operation-not-supported/2875/11

src/duplicacy_filestorage.go

@@ -12,6 +12,7 @@ import (
 	"os"
 	"path"
 	"strings"
+	"syscall"
 	"time"
 )
 
@@ -190,10 +191,13 @@ func (storage *FileStorage) UploadFile(threadIndex int, filePath string, content
 		return err
 	}
 
-	err = file.Sync()
-	if err != nil {
-		file.Close()
-		return err
+	if err = file.Sync(); err != nil {
+		pathErr, ok := err.(*os.PathError)
+		isNotSupported := ok && pathErr.Op == "sync" && pathErr.Err == syscall.ENOTSUP
+		if !isNotSupported {
+			_ = file.Close()
+			return err
+		}
 	}
 
 	err = file.Close()