[Antergos and Manjaro support] [Download latest detect_linux.sh if bundled script returns unknown] [Display error message if OS is detected as unknown]

public/detect_linux.sh

@@ -67,6 +67,9 @@ elif [ -f /etc/os-release ]; then
   . /etc/os-release
   if [ "$ID" == "arch" ]; then
     DISTNAME=arch
+  elif [ "$ID" == "antergos" ] || [ "$ID" == "manjaro" ]; then
+    DISTNAME=ubuntu
+    DISTVER=18.10
   elif [ "$ID" == "opensuse-leap" ]; then
     if [ "$VERSION_ID" == "15.0" ]; then
       DISTNAME=opensuse