opt: fix libmusl compile.

Fixes: #63
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

ccan/opt/usage.c

@@ -4,7 +4,9 @@
 #include <sys/ioctl.h>
 #include <sys/termios.h> /* Required on Solaris for struct winsize */
 #endif
+#if HAVE_SYS_UNISTD_H
 #include <sys/unistd.h> /* Required on Solaris for ioctl */
+#endif
 #include <string.h>
 #include <stdlib.h>
 #include <stdio.h>

tools/configurator/configurator.c

@@ -315,6 +315,8 @@ static struct test tests[] = {
 	  "#include <sys/filio.h>\n" },
 	{ "HAVE_SYS_TERMIOS_H", OUTSIDE_MAIN, NULL, NULL,
 	  "#include <sys/termios.h>\n" },
+	{ "HAVE_SYS_UNISTD_H", OUTSIDE_MAIN, NULL, NULL,
+	  "#include <sys/unistd.h>\n" },
 	{ "HAVE_TYPEOF", INSIDE_MAIN, NULL, NULL,
 	  "__typeof__(argc) i; i = argc; return i == argc ? 0 : 1;" },
 	{ "HAVE_UNALIGNED_ACCESS", DEFINES_EVERYTHING|EXECUTE, NULL, NULL,