Added missing argument to Linux product

Added -Dprism.forceGPU=true to the Linux product's VM arguments, as some
systems require it in order to display JavaFX graphics.
Signed-off-by: Robert Smith <SmithRW@ornl.gov>

org.eclipse.ice.repository/ice.product

@@ -3,7 +3,6 @@
 
 <product name="ICE" uid="ice.product" id="org.eclipse.ice.client.rcp.product" application="org.eclipse.ui.ide.workbench" version="2.1.8.20160208" useFeatures="true" includeLaunchers="true">
 
-
    <configIni use="default">
    </configIni>
 
@@ -14,7 +13,7 @@
       </programArgsLin>
       <vmArgs>-Dvisit.port=5600 -DREFRESH_BUNDLES=FALSE -Xmx2048M -XX:MaxPermSize=1024M -Dmax_download_size=52428800 -Dorg.eclipse.equinox.http.jetty.http.port=8080 -Dosgi.framework.extensions=org.eclipse.fx.osgi
       </vmArgs>
-      <vmArgsLin>-Dvisit.binpath=@user.home/visit/bin
+      <vmArgsLin>-Dprism.forceGPU=true -Dvisit.binpath=@user.home/visit/bin
       </vmArgsLin>
       <vmArgsMac>-XstartOnFirstThread -Dorg.eclipse.swt.internal.carbon.smallFonts -Dvisit.binpath=@user.home/visit/bin
       </vmArgsMac>
@@ -38,7 +37,6 @@
       </win>
    </launcher>
 
-
    <vm>
    </vm>