Some must-have flags

Author: grendello

src/Xamarin.Android.Build.Tasks/Utilities/NativeLinker.cs

@@ -25,11 +25,13 @@ class NativeLinker
 		"-z relro",
 		"-z noexecstack",
 		"-z max-page-size=16384",
+		"-z now", // we need it for security reasons (without it PLT can be overwritten)
 		"--enable-new-dtags",
 		"--build-id=sha1",
 		"--warn-shared-textrel",
 		"--fatal-warnings",
-		"--no-rosegment"
+		"--no-rosegment",
+		"--eh-frame-hdr", // CoreCLR needs it
 	};
 
 	readonly List<string> extraArgs = new ();

src/Xamarin.Android.Build.Tasks/Utilities/NativeRuntimeComponents.cs

@@ -96,7 +96,10 @@ public NativeRuntimeComponents (ITaskItem[] monoComponents)
 			new ClrArchive ("libcoreclr.a"),
 			new ClrArchive ("libcoreclrminipal.a"),
 			new ClrArchive ("libgc_pal.a"),
-			new ClrArchive ("libcoreclrpal.a", wholeArchive: true),
+
+			// CoreCLR links this archive whole, but it appears to work fine for us when linked in a normal way.
+			// Leave the flag commented, just in case we discover something not working right.
+			new ClrArchive ("libcoreclrpal.a"/*, wholeArchive: true*/),
 			new ClrArchive ("libeventprovider.a"),
 			new ClrArchive ("libnativeresourcestring.a"),
 			new ClrArchive ("libminipal.a"),