rip-script: append GLADE_ICON_THEME_PATH instead of overwrite

Author: hansu

scripts/rip-environment.in

@@ -68,7 +68,7 @@ LINUXCNCVERSION="@EMC2VERSION@"; export LINUXCNCVERSION
 LINUXCNC_NCFILES_DIR="@EMC2_NCFILES_DIR@"; export LINUXCNC_NCFILES_DIR
 LINUXCNC_EMCSH=@WISH@; export LINUXCNC_EMCSH
 PATH=@EMC2_BIN_DIR@:$EMC2_HOME/scripts:$EMC2_HOME/tcl:"$PATH"
-GLADE_ICON_THEME_PATH=$EMC2_HOME/share/glade/pixmaps export GLADE_ICON_THEME_PATH
+GLADE_ICON_THEME_PATH=$EMC2_HOME/share/glade/pixmaps:"$GLADE_ICON_THEME_PATH" export GLADE_ICON_THEME_PATH
 
 if [ -z "$TCLLIBPATH" ]; then
     TCLLIBPATH=$EMC2_HOME/tcl