Implement more security stuff

- Support deterministic stacks on OpenBSD
- Support OpenBSD system call origin verification
- Fix overrun by one in chibicc string token allocator
- Get all chibicc tests passing under Address Sanitizer

third_party/third_party.mk

@@ -1,15 +1,10 @@
 #-*-mode:makefile-gmake;indent-tabs-mode:t;tab-width:8;coding:utf-8-*-┐
 #───vi: set et ft=make ts=8 tw=8 fenc=utf-8 :vi───────────────────────┘
 
-# TODO(jart): make chibicc compiled chibicc work with asan runtime
-ifneq ($(MODE),dbg)
-THIRD_PARTY_CHIBICC_XXX = o/$(MODE)/third_party/chibicc
-endif
-
 .PHONY:	o/$(MODE)/third_party
 o/$(MODE)/third_party:				\
 	o/$(MODE)/third_party/blas		\
-	$(THIRD_PARTY_CHIBICC_XXX)		\
+	o/$(MODE)/third_party/chibicc		\
 	o/$(MODE)/third_party/compiler_rt	\
 	o/$(MODE)/third_party/dlmalloc		\
 	o/$(MODE)/third_party/gdtoa		\