scripts: print dotnet version after installing it

We're having a problem with a build suddenly failing[1], and the
only thing that could have changed recently is the .NET Core version.

There's a similar issue filed here[2] whose error is almost the same
as ours: [3]

[1] https://gitlab.com/DiginexGlobal/geewallet/pipelines/55116937
[2] dotnet/core#2460
[3] Error MSB4018: The "GenerateDepsFile" task failed unexpectedly. [/builds/DiginexGlobal/geewallet/src/GWallet.Backend.NetStandard/GWallet.Backend.NetStandard.fsproj]
/usr/share/dotnet/sdk/2.1.602/Sdks/Microsoft.NET.Sdk/targets/Microsoft.NET.Sdk.targets(129,5): error MSB4018: System.TypeLoadException: Could not load type of field 'Microsoft.NET.Build.Tasks.DependencyContextBuilder:_filteredPackages' (12) due to: Could not resolve type with token 01000025 from typeref (expected class 'NuGet.Packaging.Core.PackageIdentity' in assembly 'NuGet.Packaging, Version=5.0.0.6, Culture=neutral, PublicKeyToken=31bf3856ad364e35') assembly:NuGet.Packaging, Version=5.0.0.6, Culture=neutral, PublicKeyToken=31bf3856ad364e35 type:NuGet.Packaging.Core.PackageIdentity member:(null)

scripts/install_dotnet_sdk_from_microsoft_deb_packages.sh

@@ -11,3 +11,4 @@ apt install -y apt-transport-https
 apt update
 apt install -y dotnet-sdk-2.1
 
+dotnet --version