Make sure resizetized image files are writable

Fixes #23397

Commit ff5f3f0 added code which "touches" a file
to make sure its LastWrite time is up to date. This
was to help solve certain build issues.

However there was an oversight. Certain source control
systems always check out files `readonly`. In these
cases the file attributes are copied when we make a
copy of a file to be resizetized. When that happens
we end up with the following error.

```
Access to the path 'Debug\net8.0-android\resizetizer\r\drawable\foo.png' is denied.
```

To fix this lets make sure that the file is writable before
we try to update it.

Also fix some formatting to make sure it matches.

src/SingleProject/Resizetizer/src/ResizetizeImages.cs

@@ -116,8 +116,10 @@ public override System.Threading.Tasks.Task ExecuteAsync()
 				attr.Add("_ResizetizerDpiScale", img.Dpi.Scale.ToString("0.0", CultureInfo.InvariantCulture));
 
 				copiedResources.Add(new TaskItem(itemSpec, attr));
+				// Make sure the file is not readonly
+				Utils.SetWriteable(itemSpec);
 				// force the date time so we never update an image if its not changed.
-				File.SetLastWriteTimeUtc (itemSpec, DateTime.UtcNow);
+				File.SetLastWriteTimeUtc(itemSpec, DateTime.UtcNow);
 			}
 
 			CopiedResources = copiedResources.ToArray();

src/SingleProject/Resizetizer/src/Utils.cs

@@ -57,5 +57,15 @@ public static (bool Exists, DateTime Modified) FileExists(string path)
 			var modified = exists ? File.GetLastWriteTimeUtc(path) : System.DateTime.MinValue;
 			return (exists, modified);
 		}
+
+		public static void SetWriteable(string source, bool checkExists = true)
+		{
+			if (checkExists && !File.Exists(source))
+				return;
+
+			var attributes = File.GetAttributes(source);
+			if ((attributes & FileAttributes.ReadOnly) == FileAttributes.ReadOnly)
+				File.SetAttributes(source, attributes & ~FileAttributes.ReadOnly);
+		}
 	}
 }