Move ruby/assert.h include after other headers

Relocate ruby/assert.h inclusion to the end and add RUBY_DEBUG fallback if not present. Ensures correct header order and macro definition.

Author: ianks

crates/rb-sys-build/src/bindings/wrapper.h

@@ -1,8 +1,5 @@
 #include "ruby.h"
 
-#ifdef HAVE_RUBY_ASSERT_H
-#include "ruby/assert.h"
-#endif
 #ifdef HAVE_RUBY_DEBUG_H
 #include "ruby/debug.h"
 #endif
@@ -72,3 +69,9 @@
 #ifdef HAVE_RUBY_IO_BUFFER_H
 #include "ruby/io/buffer.h"
 #endif
+
+#ifdef HAVE_RUBY_ASSERT_H
+#include "ruby/assert.h"
+#else
+# define RUBY_DEBUG 0
+#endif