Enable tracing to see why CI is crashing.

Author: mjp41

CMakeLists.txt

@@ -209,6 +209,8 @@ if (SNMALLOC_NO_REALLOCARR)
   add_as_define(SNMALLOC_NO_REALLOCARR)
 endif()
 
+add_as_define(SNMALLOC_TRACING)
+
 target_compile_definitions(snmalloc INTERFACE $<$<BOOL:CONST_QUALIFIED_MALLOC_USABLE_SIZE>:MALLOC_USABLE_SIZE_QUALIFIER=const>)
 
 # In debug and CI builds, link the backtrace library so that we can get stack