rcutorture: Summarize summary of build and run results

When running the default list of tests, the run summary of a successful
(that is, failed to find any errors) run fits easily on a 24-line screen.
But a run with something like "--configs '5*CFLIST'" will be 80 lines long,
and it is all too easy to miss a failure message when scrolling back.
This commit therefore prints out the number of runs with failing builds
or runtime failures, but only if there are any such failures.

For example, a run with a single build error and a single runtime error
would print two lines like this:

1 runs with build errors.
1 runs with runtime errors.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

tools/testing/selftests/rcutorture/bin/kvm-recheck.sh

@@ -13,6 +13,9 @@
 #
 # Authors: Paul E. McKenney <paulmck@linux.ibm.com>
 
+T=/tmp/kvm-recheck.sh.$$
+trap 'rm -f $T' 0 2
+
 PATH=`pwd`/tools/testing/selftests/rcutorture/bin:$PATH; export PATH
 . functions.sh
 for rd in "$@"
@@ -68,4 +71,16 @@ do
 		fi
 	done
 done
-EDITOR=echo kvm-find-errors.sh "${@: -1}" > /dev/null 2>&1
+EDITOR=echo kvm-find-errors.sh "${@: -1}" > $T 2>&1
+ret=$?
+builderrors="`tr ' ' '\012' < $T | grep -c '/Make.out.diags'`"
+if test "$builderrors" -gt 0
+then
+	echo $builderrors runs with build errors.
+fi
+runerrors="`tr ' ' '\012' < $T | grep -c '/console.log.diags'`"
+if test "$runerrors" -gt 0
+then
+	echo $runerrors runs with runtime errors.
+fi
+exit $ret