Improve signal handling and math

- Polyfill ucontext_t on FreeBSD/OpenBSD/NetBSD
- Add tests confirming signals can edit CPU state
- Work towards supporting ZIP filesystem on bare metal
- Add more tinymath unit tests for POSIX conformance
- Add X87 and SSE status flags to crash report
- Fix some bugs in blinkenlights
- Fix llvm build breakage

build/config.mk

@@ -95,7 +95,7 @@ CONFIG_COPTS +=			\
 	$(SANITIZER)
 
 TARGET_ARCH ?=			\
-	-march=native
+	-msse3
 
 OVERRIDE_CCFLAGS +=		\
 	-fno-pie