Only run netcore tests on coreclr.

src/Compilers/CSharp/Test/Emit/CodeGen/CodeGenFunctionPointersTests.cs

@@ -7034,7 +7034,7 @@ static void M2(delegate*<ref string, ref string> ptr1)
             );
         }
 
-        [Fact]
+        [ConditionalFact(typeof(CoreClrOnly))]
         public void SpanInArgumentAndReturn()
         {
             var comp = CompileAndVerifyFunctionPointers(@"

src/Compilers/CSharp/Test/Semantic/Semantics/FunctionPointerTests.cs

@@ -2888,7 +2888,7 @@ unsafe static class C
             );
         }
 
-        [Fact, WorkItem(44953, "https://github.com/dotnet/roslyn/issues/44953")]
+        [ConditionalFact(typeof(CoreClrOnly)), WorkItem(44953, "https://github.com/dotnet/roslyn/issues/44953")]
         public void RestrictedTypeInFunctionPointer()
         {
             var comp = CreateCompilationWithFunctionPointers(@"