selftests/nolibc: integrate with kselftests

Hook up nolibc-test with the kselftests framework.
This enables CI systems and developers to easily execute the tests.

While nolibc-test does not emit KTAP output itself that is not a problem,
as the kselftest executor will wrap the output in KTAP.

Acked-by: Willy Tarreau <w@1wt.eu>
Link: https://lore.kernel.org/r/20250620-nolibc-selftests-v1-4-f6b2ce7c5071@weissschuh.net
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>

Author: t-8ch

tools/testing/selftests/Makefile

@@ -77,6 +77,7 @@ TARGETS += net/ovpn
 TARGETS += net/packetdrill
 TARGETS += net/rds
 TARGETS += net/tcp_ao
+TARGETS += nolibc
 TARGETS += nsfs
 TARGETS += pci_endpoint
 TARGETS += pcie_bwctrl