added support for Mojave

Author: jonelo

HISTORY

@@ -1,3 +1,7 @@
+October 20, 2018 v1.6
+- simplified check for macos starting with High Sierra in order not to
+  break on the successor of Mojave
+
 September 25, 2018 v1.5
 - added support for macOS Mojave
 

osxapp_vers

@@ -119,7 +119,7 @@ else
                 exit
             fi
 
-            if [[ -e "$APPNAME/Contents/SharedSupport/BaseSystem.dmg" ]]; then
+            if [ -f "$APPNAME/Contents/SharedSupport/BaseSystem.dmg" ]; then
             # Starting with High Sierra ...
                 # Mount the BaseSystem.dmg
                 hdiutil attach "$APPNAME/Contents/SharedSupport/BaseSystem.dmg" \