qfile-utils: do not write a random extra byte

readlink(2) does not write a terminating NUL, and the read side
will already place a NUL after whatever it receives.
While it seems odd that this would be buggy (ie, synlinks on
the ohter side would be pointing to the wrong filename, though
I guess if we're lucky and the stack had a 0 byte at the right
place, symlink(2) would do what was expected), my reading of
the code tells me this patch is right. Needs testing to double
check.

qubes-rpc/qfile-utils.c

@@ -175,9 +175,9 @@ int single_file_processor(const char *filename, const struct stat *st)
 		char name[st->st_size + 1];
 		if (readlink(filename, name, sizeof(name)) != st->st_size)
 			gui_fatal("readlink %s", filename);
-		hdr.filelen = st->st_size + 1;
+		hdr.filelen = st->st_size;
 		write_headers(&hdr, filename);
-		if (!write_all_with_crc(1, name, st->st_size + 1)) {
+		if (!write_all_with_crc(1, name, st->st_size)) {
 			set_block(0);
 			wait_for_result();
 			exit(1);