selftests: kselftest: Fix build failure with NOLIBC

As Mark explains ksft_min_kernel_version() can't be compiled with nolibc,
it doesn't implement uname().

Fixes: 6d029c2 ("selftests/timers/posix_timers: Reimplement check_timer_distribution()")
Reported-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20240412123536.GA32444@redhat.com
Closes: https://lore.kernel.org/all/f0523b3a-ea08-4615-b0fb-5b504a2d39df@sirena.org.uk/

Author: oleg-nesterov

tools/testing/selftests/kselftest.h

@@ -395,13 +395,18 @@ static inline __noreturn __printf(1, 2) int ksft_exit_skip(const char *msg, ...)
 static inline int ksft_min_kernel_version(unsigned int min_major,
 					  unsigned int min_minor)
 {
+#ifdef NOLIBC
+	ksft_print_msg("NOLIBC: Can't check kernel version: Function not implemented\n");
+	return 0;
+#else
 	unsigned int major, minor;
 	struct utsname info;
 
 	if (uname(&info) || sscanf(info.release, "%u.%u.", &major, &minor) != 2)
 		ksft_exit_fail_msg("Can't parse kernel version\n");
 
 	return major > min_major || (major == min_major && minor >= min_minor);
+#endif
 }
 
 #endif /* __KSELFTEST_H */