KVM: selftests: Reword the NX hugepage test's skip message to be more helpful

Rework the NX hugepage test's skip message regarding the magic token to
provide all of the necessary magic, and to very explicitly recommended
using the wrapper shell script.

Opportunistically remove an overzealous newline; splitting the
recommendation message across two lines of ~45 characters makes it much
harder to read than running out a single line to 98 characters.

Link: https://lore.kernel.org/r/20231129224042.530798-1-seanjc@google.comSigned-off-by: Sean Christopherson <seanjc@google.com>

tools/testing/selftests/kvm/x86_64/nx_huge_pages_test.c

@@ -257,9 +257,9 @@ int main(int argc, char **argv)
 	TEST_REQUIRE(kvm_has_cap(KVM_CAP_VM_DISABLE_NX_HUGE_PAGES));
 
 	__TEST_REQUIRE(token == MAGIC_TOKEN,
-		       "This test must be run with the magic token %d.\n"
-		       "This is done by nx_huge_pages_test.sh, which\n"
-		       "also handles environment setup for the test.", MAGIC_TOKEN);
+		       "This test must be run with the magic token via '-t %d'.\n"
+		       "Running via nx_huge_pages_test.sh, which also handles "
+		       "environment setup, is strongly recommended.", MAGIC_TOKEN);
 
 	run_test(reclaim_period_ms, false, reboot_permissions);
 	run_test(reclaim_period_ms, true, reboot_permissions);