Disable parallel PHAR build

This is an attempt to fix CirleCI issue in this build:
https://app.circleci.com/pipelines/github/weirdan/psalm/666/workflows/33476cb1-d753-4e2d-b067-a5c92808d725/jobs/2457

bin/build-phar.sh

@@ -14,7 +14,7 @@ if [[ ! -f build/phar-versions.php ]] ; then
    exit;
 fi
 
-vendor/bin/box compile
+vendor/bin/box compile --no-parallel
 
 if [[ "$GPG_SIGNING" != '' ]] ; then
     if [[ "$GPG_SECRET_KEY" != '' ]] ; then