Don’t try to validate trace XML when xmllint not found

This was the intended behaviour to begin with, I just forgot
to put the ‘exit’ there.

Author: hannes-steffenhagen-diffblue

regression/validate-trace-xml-schema/check.sh

@@ -13,6 +13,7 @@ fi
 xmllint="$(command -v xmllint)"
 if [ $? -ne 0 ] > /dev/null; then
     echo "xmllint not found, skipping XSD tests"
+    exit
 fi
 
 python3 check.py ../../src/cbmc/cbmc "$xmllint"