[Xamarin.Android.Build.Tasks] Files.ExtractAll timestamps

This fixes the failing test on MacOS. It appears I'm seeing diffent
behavior running on Mono, and I'm having to explicitly set the
timestamps on files being extracted from a zip.

I also couldn't use `MonoAndroidHelper`, since it's method that does
this requires the MSBuild logger.

Author: jonathanpeppers

src/Xamarin.Android.Build.Tasks/Utilities/Files.cs

@@ -245,6 +245,9 @@ public static bool ExtractAll(ZipArchive zip, string destination, Action<int, in
 				if (forceUpdate || entry.ModificationTime > dt) {
 					try {
 						entry.Extract (destination, fullName, FileMode.Create);
+						var utcNow = DateTime.UtcNow;
+						File.SetLastWriteTimeUtc (outfile, utcNow);
+						File.SetLastAccessTimeUtc (outfile, utcNow);
 					} catch (PathTooLongException) {
 						throw new PathTooLongException ($"Could not extract \"{fullName}\" to \"{outfile}\". Path is too long.");
 					}