selftests/nolibc: link_cross: use /proc/self/cmdline

For CONFIG_NET=n, there would be no /proc/self/net, so, use
/proc/self/cmdline instead.
Reviewed-by: Thomas Weißschuh <linux@weissschuh.net>
Signed-off-by: Zhangjin Wu <falcon@tinylab.org>
Signed-off-by: Willy Tarreau <w@1wt.eu>

tools/testing/selftests/nolibc/nolibc-test.c

@@ -732,7 +732,7 @@ int run_syscall(int min, int max)
 		CASE_TEST(link_root1);        EXPECT_SYSER(1, link("/", "/"), -1, EEXIST); break;
 		CASE_TEST(link_blah);         EXPECT_SYSER(1, link("/proc/self/blah", "/blah"), -1, ENOENT); break;
 		CASE_TEST(link_dir);          EXPECT_SYSER(euid0, link("/", "/blah"), -1, EPERM); break;
-		CASE_TEST(link_cross);        EXPECT_SYSER(proc, link("/proc/self/net", "/blah"), -1, EXDEV); break;
+		CASE_TEST(link_cross);        EXPECT_SYSER(proc, link("/proc/self/cmdline", "/blah"), -1, EXDEV); break;
 		CASE_TEST(lseek_m1);          EXPECT_SYSER(1, lseek(-1, 0, SEEK_SET), -1, EBADF); break;
 		CASE_TEST(lseek_0);           EXPECT_SYSER(1, lseek(0, 0, SEEK_SET), -1, ESPIPE); break;
 		CASE_TEST(mkdir_root);        EXPECT_SYSER(1, mkdir("/", 0755), -1, EEXIST); break;