[XA.Build.Tasks] Fix file hashing using statement

[pjcollins]

Context: https://dev.azure.com/devdiv/DevDiv/_releaseProgress?releaseId=469145&_a=release-environment-extension&environmentId=2323128&extensionId=ms.vss-test-web.test-result-in-release-environment-editor-tab&runId=8876788&resultId=100476&paneView=debug
Context: 88a1d6c

Adds missing braces to a using statement to fix the following
ObjectDisposedException:

C:\Program Files (x86)\Microsoft Visual Studio\2019\IntPreview\MSBuild\Xamarin\Android\Xamarin.Android.Common.targets(535,3): warning XA0121: Assembly 'Xamarin.Android.Support.Compat.dll' is using a deprecated attribute '[assembly: Java.Interop.JavaLibraryReferenceAttribute]'. Use a newer version of this NuGet package or notify the library author. [C:\agent\_work\r1\a\mc\N-02-KittenView\KittenView.Droid\KittenView.Droid.csproj]
  Making sure we have https://dl-ssl.google.com/android/repository/android_m2repository_r38.zip downloaded and extracted m2repository/com/android/support/support-compat/24.2.1/support-compat-24.2.1.aar from it... (TaskId:126)
C:\Program Files (x86)\Microsoft Visual Studio\2019\IntPreview\MSBuild\Xamarin\Android\Xamarin.Android.Common.targets(535,3): error : Cannot access a disposed object. [C:\agent\_work\r1\a\mc\N-02-KittenView\KittenView.Droid\KittenView.Droid.csproj]
C:\Program Files (x86)\Microsoft Visual Studio\2019\IntPreview\MSBuild\Xamarin\Android\Xamarin.Android.Common.targets(535,3): error :    at System.Security.Cryptography.HashAlgorithm.ComputeHash(Stream inputStream) [C:\agent\_work\r1\a\mc\N-02-KittenView\KittenView.Droid\KittenView.Droid.csproj]
C:\Program Files (x86)\Microsoft Visual Studio\2019\IntPreview\MSBuild\Xamarin\Android\Xamarin.Android.Common.targets(535,3): error :    at Xamarin.Android.Tools.Files.HashFile(String filename, HashAlgorithm hashAlg) [C:\agent\_work\r1\a\mc\N-02-KittenView\KittenView.Droid\KittenView.Droid.csproj]
C:\Program Files (x86)\Microsoft Visual Studio\2019\IntPreview\MSBuild\Xamarin\Android\Xamarin.Android.Common.targets(535,3): error :    at Xamarin.Android.Tasks.GetAdditionalResourcesFromAssemblies.IsValidDownload(String file, String sha1) [C:\agent\_work\r1\a\mc\N-02-KittenView\KittenView.Droid\KittenView.Droid.csproj]
C:\Program Files (x86)\Microsoft Visual Studio\2019\IntPreview\MSBuild\Xamarin\Android\Xamarin.Android.Common.targets(535,3): error :    at Xamarin.Android.Tasks.GetAdditionalResourcesFromAssemblies.MakeSureLibraryIsInPlace(String destinationBase, String url, String version, String embeddedArchive, String sha1) [C:\agent\_work\r1\a\mc\N-02-KittenView\KittenView.Droid\KittenView.Droid.csproj]
C:\Program Files (x86)\Microsoft Visual Studio\2019\IntPreview\MSBuild\Xamarin\Android\Xamarin.Android.Common.targets(535,3): error :    at Xamarin.Android.Tasks.GetAdditionalResourcesFromAssemblies.AddAttributeValue(ICollection`1 items, CustomAttributeValue`1 attributeValue, String errorCode, String errorFmt, Boolean isDirectory, String fullPath, String attributeFullName) [C:\agent\_work\r1\a\mc\N-02-KittenView\KittenView.Droid\KittenView.Droid.csproj]
C:\Program Files (x86)\Microsoft Visual Studio\2019\IntPreview\MSBuild\Xamarin\Android\Xamarin.Android.Common.targets(535,3): error :    at Xamarin.Android.Tasks.GetAdditionalResourcesFromAssemblies.<RunTaskAsync>d__38.MoveNext() [C:\agent\_work\r1\a\mc\N-02-KittenView\KittenView.Droid\KittenView.Droid.csproj]
Done executing task "GetAdditionalResourcesFromAssemblies" -- FAILED. (TaskId:126)

[brendanzagaeski]

Release status update

A new Preview version has now been published that includes the fix from this item.

Fix included in Xamarin.Android 10.1.0.29.

Fix included on Windows in Visual Studio 2019 version 16.4 Preview 3. To try the Preview version that includes the fix, check for the latest updates in Visual Studio Preview.

Fix included on macOS in Visual Studio 2019 for Mac version 8.4 Preview 2. To try the Preview version that includes the fix, check for the latest updates on the Preview updater channel.