ci: fix DOS error code propagation bug by exporting environment varia…

…ble, so the if-statement further below has it in its context

.github/workflows/02-pr-checks.yml

@@ -78,10 +78,10 @@ jobs:
           /usr/local/bin/run_cicd_dos.sh
           # Propagate error code from DOS test or exit with error code 254 if the exit code file is missing
           echo step1
-          dos_exit_code=$(cat test/exitcode.txt || echo 254)
+          export dos_exit_code=$(cat test/exitcode.txt || echo 254)
           echo DOS exit code was $dos_exit_code
           echo step2
-          if [ $dos_exit_code -ne 0 ]; then exit $dos_exit_code; fi
+          sh -c 'if [ $dos_exit_code -ne 0 ]; then exit $dos_exit_code; fi'
           echo step3
           wget -P /tmp https://aluigi.altervista.org/mytoolz/dtmf2num.zip
           echo "187d43e4d57535da3386eee3accdbcd09526378e3258db7f1bd5afccd0c64360  /tmp/dtmf2num.zip" | sha256sum -c