Don't apply optimization on non-AOT builds, e.g. simulators, since some

features (like XML serialization) checks for
`RuntimeFeature.IsDynamicCodeSupported` and that requires some types
to be subclassed thru SRE

dotnet/targets/Xamarin.Shared.Sdk.targets

@@ -467,7 +467,7 @@
 			<_ExtraTrimmerArgs>$(_ExtraTrimmerArgs) --disable-opt unusedtypechecks</_ExtraTrimmerArgs>
 
 			<!-- If a release build and the app is not extensible (no interpreter or JIT/code-loading for macOS) then the sealer optimization can be used -->
-			<_ExtraTrimmerArgs Condition="'$(_BundlerDebug)' != 'true' And '$(MtouchInterpreter)' == '' And '$(_PlatformName)' != 'macOS'">$(_ExtraTrimmerArgs) --enable-opt sealer</_ExtraTrimmerArgs>
+			<_ExtraTrimmerArgs Condition="'$(_BundlerDebug)' != 'true' And '$(MtouchInterpreter)' == '' And '$(_RunAotCompiler)' == 'true' And '$(_PlatformName)' != 'macOS'">$(_ExtraTrimmerArgs) --enable-opt sealer</_ExtraTrimmerArgs>
 
 			<!-- We always want the linker to process debug symbols, even when building in Release mode, because the AOT compiler uses the managed debug symbols to output DWARF debugging symbols -->
 			<TrimmerRemoveSymbols Condition="'$(TrimmerRemoveSymbols)' == ''">false</TrimmerRemoveSymbols>

tests/linker/ios/link all/SealerTest.cs

@@ -36,6 +36,17 @@ public class Subclass : Base, Interface {
 	[Preserve (AllMembers = true)]
 	public class SealerTest {
 
+#if NET
+		[SetUp]
+		public void SetUp ()
+		{
+			// XML serialization mechanism is controlled by RuntimeFeature.IsDynamicCodeSupported
+			// which will be true for simulator / JIT builds
+			// so the optimization is disabled unless AOT is used
+			TestRuntime.AssertDevice ();
+		}
+#endif
+
 		[Test]
 		public void Sealed ()
 		{