api: add further is_supported_system optimizations

was supposed to be included in 0952537

api

@@ -2570,7 +2570,7 @@ Specifically, the issue is $(wc -l <<<"$frankendebian" | grep -q 1 && echo 'this
     echo "Congratulations, Linux tinkerer, you broke your system. The init package can not be found, which means you have removed the default debian sources from your system.
 All apt based application installs will fail. Unless you have a backup of your /etc/apt/sources.list /etc/apt/sources.list.d you will need to reinstall your OS."
     return 1
-  elif [ -z "$(apt-get indextargets --no-release-info --format '$(SITE) $(RELEASE) $(TARGET_OF)' | sort -u | awk '{if ($3=="deb") print $1" "$2 }')" ];then
+  elif [ -z "$DEFAULT_REPOS" ];then
     echo "Congratulations, Linux tinkerer, you broke your system. You have removed ALL debian sources from your system.
 All apt based application installs will fail. Unless you have a backup of your /etc/apt/sources.list /etc/apt/sources.list.d you will need to reinstall your OS."
     return 1