Build with ASAN on macOS by default.

tmux.c

@@ -49,6 +49,24 @@ static char		*make_label(const char *, char **);
 static int		 areshell(const char *);
 static const char	*getshell(void);
 
+#ifdef ASAN
+__attribute__((used)) const char *__asan_default_options(void);
+__attribute__((used)) const char *
+__asan_default_options(void)
+{
+	return (
+	    "abort_on_error=1:"
+	    "halt_on_error=1:"
+	    "detect_leaks=0:"
+	    "detect_stack_use_after_return=1:"
+	    "strict_string_checks=1:"
+	    "check_initialization_order=1:"
+	    "log_path=/tmp/tmux-asan:"
+	    "log_exe_name=1"
+	);
+}
+#endif
+
 static __dead void
 usage(int status)
 {