Use RuntimeInformation to determine the Processor architecture. (#108)

See https://docs.microsoft.com/en-us/dotnet/api/system.runtime.interopservices.architecture?view=net-6.0
Now that we ship an arm based native library on windows we need to be
able to determine the underlying library to load. We can use the
`RuntimeInformation.ProcessArchitecture` value to get this data.
Then based on that we can load from `x86`, `x64` or `arm64` subdirectories.
Note we will still fallback to loading from the current directory , but
the preference is to load from on of the architecture specific sub directories.

Author: dellis1972

LibZipSharp/Xamarin.LibZipSharp.targets

@@ -4,13 +4,13 @@
  </PropertyGroup>
  <ItemGroup>
  <_LibZipNativeLibsInclude="$(MSBuildThisFileDirectory)..\runtimes\win-x64\native\libZipSharpNative.*">
- <Link>lib64\%(FileName)%(Extension)</Link>
+ <Link>x64\%(FileName)%(Extension)</Link>
  </_LibZipNativeLibs>
  <_LibZipNativeLibsInclude="$(MSBuildThisFileDirectory)..\runtimes\win-arm64\native\libZipSharpNative.*">
- <Link>%(FileName)%(Extension)</Link>
+ <Link>arm64\%(FileName)%(Extension)</Link>
  </_LibZipNativeLibs>
  <_LibZipNativeLibsInclude="$(MSBuildThisFileDirectory)..\runtimes\win-x86\native\libZipSharpNative.*">
- <Link>%(FileName)%(Extension)</Link>
+ <Link>x86\%(FileName)%(Extension)</Link>
  </_LibZipNativeLibs>
  <_LibZipNativeLibsInclude="$(MSBuildThisFileDirectory)..\runtimes\osx\native\libZipSharpNative.dylib">
  <Link>%(FileName)%(Extension)</Link>

LibZipSharp/Xamarin.Tools.Zip/Native.cs

@@ -455,7 +455,17 @@ static Native ()
 {
 if(Environment.OSVersion.Platform==PlatformID.Win32NT){
 stringexecutingDirectory=System.IO.Path.GetDirectoryName(typeof(Native).Assembly.Location);
-SetDllDirectory(Environment.Is64BitProcess?System.IO.Path.Combine(executingDirectory,"lib64"):executingDirectory);
+	#if !NET45
+stringarch=RuntimeInformation.ProcessArchitecture.ToString().ToLower();
+stringpath=System.IO.Path.Combine(executingDirectory,arch);
+	#else
+stringpath=System.IO.Path.Combine(executingDirectory,Environment.Is64BitProcess?"x64":"x86");
+	#endif
+if(System.IO.Directory.Exists(path)){
+SetDllDirectory(path);
+return;
+}
+SetDllDirectory(executingDirectory);
 }
 }
 }