selftests/nolibc: avoid warnings during intptr tests

Recent fix ceb528fe ("selftests/nolibc: avoid gaps in test numbers")
had the annoying side effect of always returning skipped tests, which
are normally supposed to happen only when certain features are missing
to run the test (missing kernel options, toolchain not supporting
stack-protector etc). As such there are now always warnings. Let's
modify the test to not use the condition and instead use a ternary
expression to check the result.

Fixes: ceb528fe ("selftests/nolibc: avoid gaps in test numbers")
Cc: Thomas WeiÃ<9F>schuh <linux@weissschuh.net>
Signed-off-by: Willy Tarreau <w@1wt.eu>