Roll buildroot to switch to VS 2019

DEPS

@@ -105,7 +105,7 @@ allowed_hosts = [
 ]
 
 deps = {
-  'src': 'https://github.com/flutter/buildroot.git' + '@' + 'f83d1d75216e97fb696434bca1cb9a4e7a570fb6',
+  'src': 'https://github.com/stuartmorgan/buildroot.git' + '@' + '636b23c76c3f18c14341077c1b61bb90395f85b4',
 
    # Fuchsia compatibility
    #

shell/platform/windows/win32_window_proc_delegate_manager_unittests.cc

@@ -38,6 +38,12 @@ bool TestWindowProcCallback2(HWND hwnd,
                              LPARAM lparam,
                              void* user_data,
                              LRESULT* result) {
+  // This line exists so that this function is not just a straight passthrough,
+  // since in some cases the compiler was optimizing it away and causing the two
+  // registrations in RegisterMultiple to actually have the same function
+  // address.
+  EXPECT_NE(reinterpret_cast<unsigned long>(TestWindowProcCallback),
+            reinterpret_cast<unsigned long>(TestWindowProcCallback2));
   return TestWindowProcCallback(hwnd, message, wparam, lparam, user_data,
                                 result);
 }