clang: Disable source order sorting for now. (#2558)

* clang: Clean up source order sorting.

This doesn't change behavior but is easier to debug and reason about
(because you have the relevant cursors there).

* clang: Disable source order sorting for now.

This disables (hopefully temporarily) source order sorting, for causing
correctness regressions like #2556.

Fixes #2556.

* tests: Add a test for #2556

* Remove merge artifact

* Update clang.rs

---------

Co-authored-by: Christian Poveda Ruiz <[email protected]>

Author: emilio

bindgen-tests/tests/expectations/tests/allowlist-file.rs

@@ -0,0 +1,4 @@
+// bindgen-flags: --enable-cxx-namespaces -- -x c++ -Itests/headers -include tests/headers/issue-2556/nsStyleStruct.h -include tests/headers/issue-2556/LayoutConstants.h
+
+#include "issue-2556/nsSize.h"
+#include "issue-2556/nsStyleStruct.h"

bindgen-tests/tests/expectations/tests/issue-2556.rs

@@ -0,0 +1,7 @@
+#include "nsSize.h"
+
+namespace foo {
+
+static constexpr nsSize kFallbackIntrinsicSize(0, 0);
+
+}

bindgen-tests/tests/expectations/tests/jsval_layout_opaque.rs

@@ -0,0 +1,6 @@
+#pragma once
+
+struct nsSize {
+  int width, height;
+  constexpr nsSize(int aWidth, int aHeight) : width(aWidth), height(aHeight) {}
+};

bindgen-tests/tests/expectations/tests/jsval_layout_opaque_1_0.rs

@@ -0,0 +1,3 @@
+#pragma once
+
+#include "nsSize.h"