ktest.pl: Check kernelrelease return in get_version

In the case of a test that uses the special option ${KERNEL_VERSION} in one
of its settings but has no configuration available in ${OUTPUT_DIR}, for
example if it's a new empty directory, then the `make kernelrelease` call
will fail and the subroutine will chomp an empty string, silently. Fix that
by adding an empty configuration and retrying.

Cc: stable@vger.kernel.org
Cc: John Hawley <warthog9@eaglescrag.net>
Fixes: 5f9b6ce ("ktest: Bisecting, install modules, add logging")
Link: https://lore.kernel.org/20241205-ktest_kver_fallback-v2-1-869dae4c7777@suse.com
Signed-off-by: Ricardo B. Marliere <rbm@suse.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

Author: rbmarliere

tools/testing/ktest/ktest.pl

@@ -2419,6 +2419,11 @@ sub get_version {
     return if ($have_version);
     doprint "$make kernelrelease ... ";
     $version = `$make -s kernelrelease | tail -1`;
+    if (!length($version)) {
+	run_command "$make allnoconfig" or return 0;
+	doprint "$make kernelrelease ... ";
+	$version = `$make -s kernelrelease | tail -1`;
+    }
     chomp($version);
     doprint "$version\n";
     $have_version = 1;