Fix MonoMod/MonoMod#93

Author: punchready

RuntimeDetour/Platforms/Runtime/DetourRuntimeNETCore30Platform.cs

@@ -179,6 +179,8 @@ protected unsafe CorJitResult CompileMethodHook(
             out byte* nativeEntry, 
             out uint nativeSizeOfCode) {
 
+            int _lastError = Marshal.GetLastPInvokeError();
+
             nativeEntry = null;
             nativeSizeOfCode = 0;
 
@@ -223,6 +225,8 @@ protected unsafe CorJitResult CompileMethodHook(
                     }
                 }
 
+                Marshal.SetLastPInvokeError(_lastError);
+                
                 return result;
             } finally {
                 hookEntrancy--;