Don't relocate file descriptor memory

This change fixes #496 where ASAN spotted a race condition that could
happen in multithreaded programs, with more than OPEN_MAX descriptors
when using ZipOS or Windows NT, which require tracking open file info
and this change fixes that table so it never relocates, thus allowing
us to continue to enjoy the benefits of avoiding locks while reading.

libc/intrin/intrin.mk

@@ -43,6 +43,20 @@ $(LIBC_INTRIN_A).pkg:					\
 		$(LIBC_INTRIN_A_OBJS)			\
 		$(foreach x,$(LIBC_INTRIN_A_DIRECTDEPS),$($(x)_A).pkg)
 
+# we can't use asan because:
+#   asan guard pages haven't been allocated yet
+o/$(MODE)/libc/intrin/directmap.o			\
+o/$(MODE)/libc/intrin/directmap-nt.o: private		\
+		OVERRIDE_COPTS +=			\
+			-ffreestanding			\
+			-fno-sanitize=address
+
+# we want small code size because:
+#   to keep .text.head under 4096 bytes
+o/$(MODE)/libc/intrin/mman.greg.o: private		\
+		OVERRIDE_COPTS +=			\
+			-Os
+
 # we can't use asan and ubsan because:
 #   this is asan and ubsan
 o/$(MODE)/libc/intrin/asan.o				\