Fix assert definition

include/bits/assert.h

-#ifndef _BITS_ASSERT_H
-#define _BITS_ASSERT_H
+// Do not use include guard, to ensure assert is always defined
+#ifdef assert
+#undef assert
+#endif
 
 #ifdef NDEBUG
 # define assert(cond) (void) 0
@@ -7,5 +9,3 @@
 # define assert(cond) \
   ((void)((cond) || (__assert_fail(__func__, __FILE__, __LINE__, #cond), 0)))
 #endif
-
-#endif

src/header/assert/cbindgen.toml

-sys_includes = ["bits/assert.h"]
+sys_includes = []
 include_guard = "_RELIBC_ASSERT_H"
+trailer = "#include <bits/assert.h>"
 language = "C"
 style = "Tag"
 no_includes = true