Fix NetBSD build.

lib/sys/sys+netbsd-x64.myr

@@ -853,7 +853,7 @@ pkg sys =
 	const close	: (fd:fd -> int64)
 	const creat	: (path:byte[:], mode:int64 -> fd)
 	const unlink	: (path:byte[:] -> int)
-	const rmdir	: (path:byte[:] -> int)
+	const rmdir	: (path:byte# -> int)
 	const read	: (fd:fd, buf:byte[:] -> size)
 	const pread	: (fd:fd, buf:byte[:], off : off -> size)
 	const readv	: (fd:fd, iov:iovec[:] -> size)
@@ -908,6 +908,7 @@ pkg sys =
 		new : void#, newsz : size# \
 		-> int)
 
+	extern const cstring	: (str : byte[:] -> byte#)
 	/* filled by start code */
 	extern var __cenvp : byte##
 ;;
@@ -918,7 +919,6 @@ the same as casting, but more concise than (writing : int64)
 */
 generic a = {x : @t; -> (x : uint64)}
 
-extern const cstring	: (str : byte[:] -> byte#)
 extern const alloca	: (sz : size	-> byte#)
 
 /* process management */