fd49fcb229
In a non-thread build, using &_ram_end as the top-of-stack is no longer correct because the stack is not always at the very top end of RAM. See eg 04c7cdb668cc7ee391ef5fe000f825389197f7e2 and 378659209778a1bde24e9b15793087023b02bbd9. The correct value to use is &_estack, which is the value stored in MP_STATE_THREAD(stack_top), and using the same code for both thread and non-thread builds makes the code cleaner.