[tests][link sdk] Re-enable test for Ping for dotnet

ref: dotnet/runtime#41355

Unlike what we have today for legacy support for Ping was added in
dotnet/runtime#52240

tests/linker/ios/link sdk/DllImportTest.cs

@@ -75,19 +75,21 @@ public void Sqlite3 ()
 			}
 		}
 
-#if NET
-		[Ignore ("https://github.com/dotnet/runtime/issues/41355")]
-#endif
 		[Test]
-		public void LackOfCapget ()
+		public void PingSend ()
 		{
-			// OSX/iOS libc (libSystem.dylib) does not have a capget - which breaks dlsym=false (required for tvOS)
-			// iOS (tvOS/watchOS) does not support Process to run ping either so it ends up with a InvalidOperationException
-			// which is now "optimized" to reduce code size (and remove DllImport) until we implement ping (see: #964)
 			var p = new Ping ();
 #if __WATCHOS__
+			// no socket support
 			Assert.Throws<PlatformNotSupportedException> (delegate { p.Send ("localhost"); });
+#elif NET
+			// support was implemented with https://github.com/dotnet/runtime/pull/52240
+			var reply = p.Send ("localhost");
+			Assert.That (reply.Status, Is.EqualTo (IPStatus.Success), "Pong");
 #else
+			// OSX/iOS libc (libSystem.dylib) does not have a capget - which breaks dlsym=false (required for tvOS)
+			// iOS (tvOS/watchOS) does not support Process to run ping either so it ends up with a InvalidOperationException
+			// which is now "optimized" to reduce code size (and remove DllImport) until we implement ping (see: #964)
 			Assert.Throws<InvalidOperationException> (delegate { p.Send ("localhost"); });
 #endif
 		}