[dotnet] Put packages (.ipa/.pkg) in the publish directory by default. (#13436)

Partial fix for #12997.

dotnet/targets/Xamarin.Shared.Sdk.Publish.targets

@@ -4,6 +4,10 @@
 		<PropertyGroup>
 			<BuildIpa Condition="'$(_PlatformName)' == 'iOS' Or '$(_PlatformName)' == 'tvOS'">true</BuildIpa>
 			<CreatePackage Condition="'$(_PlatformName)' == 'macOS' Or '$(_PlatformName)' == 'MacCatalyst'">true</CreatePackage>
+
+			<!-- Put packages in the publish directory unless asked to do otherwise -->
+			<IpaPackageDir Condition="'$(IpaPackageDir)' == '' And '$(IpaPackagePath)' == ''">$(PublishDir)</IpaPackageDir>
+			<PkgPackageDir Condition="'$(PkgPackageDir)' == '' And '$(PkgPackagePath)' == ''">$(PublishDir)</PkgPackageDir>
 		</PropertyGroup>
 	</Target>
 	<Target Name="Publish" DependsOnTargets="_PrePublish;Build">

msbuild/Xamarin.Shared/Xamarin.Shared.targets

@@ -2275,6 +2275,9 @@ Copyright (C) 2018 Microsoft. All rights reserved.
 	</Target>
 
 	<Target Name="_CreateInstaller" Condition="'$(CreatePackage)' == 'true' And '$(_CanOutputAppBundle)' == 'true'" DependsOnTargets="Codesign;_CompileProductDefinition;_WriteAppManifest">
+		<PropertyGroup>
+			<PkgPackageDir Condition="'$(PkgPackageDir)' == ''">$(TargetDir)</PkgPackageDir>
+		</PropertyGroup>
 		<CreateInstallerPackage
 			SessionId="$(BuildSessionId)"
 			Condition="'$(IsMacEnabled)' == 'true'"
@@ -2283,7 +2286,7 @@ Copyright (C) 2018 Microsoft. All rights reserved.
 			EnablePackageSigning="$(EnablePackageSigning)"
 			MainAssembly="$(TargetPath)"
 			Name="$(AssemblyName)"
-			OutputDirectory="$(TargetDir)"
+			OutputDirectory="$(PkgPackageDir)"
 			PackageSigningKey="$(PackageSigningKey)"
 			PackagingExtraArgs="$(PackagingExtraArgs)"
 			PkgPackagePath="$(PkgPackagePath)"