Fix a race in ktest-all and improve output

Turns out I broke it on last commit when there is more than one kernel to test,
both processes were attempting to read from stdin, so revert that and fix it
differently.

While here, improve some idioms and collect errored out commands to be printed
in the end, should make people less angry in the future when stuff just "fails".

ktest-all.sh

@@ -1,41 +1,46 @@
 #!/bin/bash
 
-Script=${0##*/}
-
 set -euo pipefail
 
 kprobe_only=(linux-3.10.0-123.el7.x86_64)
 result=""
+error_run=""
 declare -i failures=0
+all_kernels="$(find kernel-images/{amd64,arm64} -type f)"
 
 function maybe_kflag
 {
 	for k in "${kprobe_only[@]}"; do
 		if [ "$1" = "$k" ]; then
-			echo "-k"
 			return 0
 		fi
 	done
 
 	return 1
 }
 
-mkdir -p kernel-images/{amd64,arm64}
-
-while IFS= read -r -d '' k
+for k in $all_kernels
 do
 	kname="$(basename "$k")"
-	echo testing "$kname"
-	if ./krun.sh initramfs.gz "$k" quark-test "$(maybe_kflag "$kname")"; then
+	cmdline="./krun.sh initramfs.gz $k quark-test"
+	if maybe_kflag "$kname"; then
+		cmdline+=" -k"
+	fi
+	if eval "$cmdline"; then
 		r="$(printf "%s: ok" "$kname")"
 	else
 		r="$(printf "%s: fail" "$kname")"
+		error_run+="${cmdline}"$'\n'
 		failures=$((failures+1))
 	fi
-	result="${result}${r}\n"
-done < <(find kernel-images/{amd64,arm64} -type f -print0)
+	result+="${r}"$'\n'
+done
 
-echo -ne "$result"
+echo -n "$result"
 echo failures $failures
+if test -n "$error_run"; then
+	echo to reproduce failed cases, run:
+	echo -n "$error_run"
+fi
 
 exit $failures