[dotnet] Make relase builds for desktop universal by default. Fixes d…

…otnet#15620.

ARM64-based macOS machines are becoming more and more common, and as such it
makes sense to include ARM64 builds in the app bundle when building for
release.

Universal builds are much slower than single-architecture builds, which is why
we don't make debug builds universal.

Fixes dotnet#15620.

dotnet/targets/Xamarin.Shared.Sdk.props

@@ -38,6 +38,7 @@
 
 	<!-- Set the default RuntimeIdentifier if not already specified. -->
 	<PropertyGroup Condition="'$(_RuntimeIdentifierIsRequired)' == 'true' And '$(RuntimeIdentifier)' == '' And '$(RuntimeIdentifiers)' == '' ">
+		<!-- The _<platform>RuntimeIdentifier values are set from the IDE -->
 		<RuntimeIdentifier Condition="'$(_PlatformName)' == 'iOS'">$(_iOSRuntimeIdentifier)</RuntimeIdentifier>
 		<RuntimeIdentifier Condition="'$(_PlatformName)' == 'tvOS'">$(_tvOSRuntimeIdentifier)</RuntimeIdentifier>
 		<RuntimeIdentifier Condition="'$(_PlatformName)' == 'macOS'">$(_macOSRuntimeIdentifier)</RuntimeIdentifier>
@@ -47,8 +48,12 @@
 
 		<RuntimeIdentifier Condition="'$(RuntimeIdentifier)' == '' And '$(_PlatformName)' == 'iOS'">iossimulator-x64</RuntimeIdentifier>
 		<RuntimeIdentifier Condition="'$(RuntimeIdentifier)' == '' And '$(_PlatformName)' == 'tvOS'">tvossimulator-x64</RuntimeIdentifier>
-		<RuntimeIdentifier Condition="'$(RuntimeIdentifier)' == '' And '$(_PlatformName)' == 'macOS'">osx-x64</RuntimeIdentifier>
-		<RuntimeIdentifier Condition="'$(RuntimeIdentifier)' == '' And '$(_PlatformName)' == 'MacCatalyst'">maccatalyst-x64</RuntimeIdentifier>
+
+		<!-- For release desktop builds we default to universal apps in .NET 7+ -->
+		<RuntimeIdentifier Condition="'$(RuntimeIdentifier)' == '' And '$(Configuration)' != 'Release' And $(_PlatformName)' == 'macOS'">osx-x64</RuntimeIdentifier>
+		<RuntimeIdentifier Condition="'$(RuntimeIdentifier)' == '' And '$(Configuration)' != 'Release' And $(_PlatformName)' == 'MacCatalyst'">maccatalyst-x64</RuntimeIdentifier>
+		<RuntimeIdentifiers Condition="'$(RuntimeIdentifier)' == '' And '$(Configuration)' == 'Release' And $(_PlatformName)' == 'macOS'">osx-x64;osx-arm64</RuntimeIdentifiers>
+		<RuntimeIdentifiers Condition="'$(RuntimeIdentifier)' == '' And '$(Configuration)' == 'Release' And $(_PlatformName)' == 'MacCatalyst'">maccatalyst-x64;maccatalyst-arm64</RuntimeIdentifiers>
 		<!--
 			Workaround/hack: