Rationalize backtrace logging

GDB backtrace generated via "thread apply all bt full" is too long for
standard output, lets save them to .txt file among other log files.

bin/tests/system/run.sh.in

@@ -246,11 +246,15 @@ else
     exit $status
 fi
 
+get_core_dumps() {
+    find "$systest/" \( -name 'core*' -or -name '*.core' \) ! -name '*.gz' ! -name '*.txt' | sort
+}
+
 if [ $status != 0 ]; then
     echofail "R:$systest:FAIL"
     # Do not clean up - we need the evidence.
 else
-    core_dumps="$(find "$systest/" -name 'core*' -or -name '*.core' | sort | tr '\n' ' ')"
+    core_dumps=$(get_core_dumps | tr '\n' ' ')
     assertion_failures=$(find "$systest/" -name named.run -print0 | xargs -0 grep "assertion failure" | wc -l)
     sanitizer_summaries=$(find "$systest/" -name 'tsan.*' | wc -l)
     if [ -n "$core_dumps" ]; then
@@ -258,17 +262,28 @@ else
         echoinfo "I:$systest:Test claims success despite crashes: $core_dumps"
         echofail "R:$systest:FAIL"
         # Do not clean up - we need the evidence.
-	find "$systest/" -name 'core*' -or -name '*.core' | while read -r coredump; do
+	get_core_dumps | while read -r coredump; do
 		export SYSTESTDIR="$systest"
-		echoinfo "D:$systest:backtrace from $coredump start"
-		binary=$(gdb --batch --core="$coredump" | sed -ne "s/Core was generated by \`//;s/ .*'.$//p;")
+		echoinfo "D:$systest:backtrace from $coredump:"
+		echoinfo "D:$systest:--------------------------------------------------------------------------------"
+		binary=$(gdb --batch --core="$coredump" 2>/dev/null | sed -ne "s/Core was generated by \`//;s/ .*'.$//p;")
+		"${top_builddir}/libtool" --mode=execute gdb \
+					  -batch \
+					  -ex bt \
+					  -core="$coredump" \
+					  -- \
+					  "$binary" 2>/dev/null | sed -n '/^Core was generated by/,$p' | cat_d
+		echoinfo "D:$systest:--------------------------------------------------------------------------------"
+		coredump_backtrace=$(basename "${coredump}")-backtrace.txt
+		echoinfo "D:$systest:full backtrace from $coredump saved in $coredump_backtrace"
 		"${top_builddir}/libtool" --mode=execute gdb \
-					  --batch \
-					  --command=run.gdb \
-					  --core="$coredump" \
+					  -batch \
+					  -command=run.gdb \
+					  -core="$coredump" \
 					  -- \
-					  "$binary"
-		echoinfo "D:$systest:backtrace from $coredump end"
+					  "$binary" > "$coredump_backtrace" 2>&1
+		echoinfo "D:$systest:core dump $coredump archived as $coredump.gz"
+		gzip -1 "${coredump}"
 	done
     elif [ "$assertion_failures" -ne 0 ]; then
         status=1
@@ -283,14 +298,12 @@ else
         echofail "R:$systest:FAIL"
     else
         echopass "R:$systest:PASS"
-        if $clean
-        then
+        if $clean; then
             ( cd "${systest}" && $SHELL clean.sh "$@" )
 	    if [ "${srcdir}" != "${builddir}" ]; then
 		rm -rf "./${systest}" ## FIXME (this also removes compiled binaries)
 	    fi
-            if test -d ${srcdir}/../../../.git
-            then
+            if test -d ${srcdir}/../../../.git; then
                 git status -su --ignored "${systest}" 2>/dev/null | \
                 sed -n -e 's|^?? \(.*\)|I:file \1 not removed|p' \
                 -e 's|^!! \(.*/named.run\)$|I:file \1 not removed|p' \