remove java.ext.dirs on startup (fixes #4608)

build/build.xml

@@ -559,6 +559,9 @@
       <!-- avoid conflicts with JNA DLLs already in the path -->
       <option value="-Djna.nosys=true" />
 
+      <!-- deal with jokers who install JOGL, ANTLR, etc system-wide -->
+      <option value="-Djava.ext.dirs=lib/ext" />
+
       <option value="-Dapple.laf.useScreenMenuBar=true" />
       <option value="-Dcom.apple.macos.use-file-dialog-packages=true" />
       <option value="-Dcom.apple.macos.useScreenMenuBar=true" />

build/linux/processing

@@ -104,7 +104,7 @@ cmd_name='processing-java'
 
 if [ $current_name = $cmd_name ]
 then
-    java -Djna.nosys=true -Xmx256m processing.mode.java.Commander "$@"
+    java -Djna.nosys=true -Djava.ext.dirs=lib/ext -Xmx256m processing.mode.java.Commander "$@"
     exit $?
 else
   # Start Processing in the same directory as this script
@@ -115,5 +115,5 @@ else
   fi
   cd "$APPDIR"
 
-  java -splash:lib/about-1x.png -Djna.nosys=true -Xmx256m processing.app.Base "$SKETCH" &
+  java -splash:lib/about-1x.png -Djna.nosys=true -Djava.ext.dirs=lib/ext -Xmx256m processing.app.Base "$SKETCH" &
 fi

build/windows/config-cmd.xml

@@ -29,6 +29,8 @@
 
   <jre>
     <path>java</path>
+    <!-- Deal with jokers who install JOGL, ANTLR, etc system-wide -->
+    <opt>-Djava.ext.dirs=lib/ext</opt>
     <!-- Prevent a user-installed JNA from conflicting with our version.
          https://github.com/processing/processing/issues/2239 -->
     <opt>-Djna.nosys=true</opt>

build/windows/config.xml

@@ -26,6 +26,8 @@
   </classPath>
   <jre>
     <path>java</path>
+    <!-- Deal with jokers who install JOGL, ANTLR, etc system-wide -->
+    <opt>-Djava.ext.dirs=lib/ext</opt>
     <!-- https://github.com/processing/processing/issues/2239 -->
     <opt>-Djna.nosys=true</opt>
     <!-- Because nosys is set to true, the DLL in the current working