handle shell variables in a package name

bin/install_packages

@@ -5,7 +5,7 @@
 # install_packages -- read package config and install packages via apt-get
 #
 # This script is part of FAI (Fully Automatic Installation)
-# (c) 2000-2018, Thomas Lange, lange@informatik.uni-koeln.de
+# (c) 2000-2019, Thomas Lange, lange@informatik.uni-koeln.de
 # (c) 2003-2004, Henning Glawe, glaweh@physik.fu-berlin.de
 # (c) 2004     , Jonas Hoffmann, jhoffman@physik.fu-berlin.de
 # PRELOAD feature from Thomas Gebhardt  <gebhardt@hrz.uni-marburg.de>
@@ -526,6 +526,16 @@ sub clean_pkg_list {
       insert_pkg($n, $pack, 1, "$n using $pack found") && next;
     }
 
+    # handle $varname in package name
+    if ( $pack =~ s/\$\w+//) {
+      insert_pkg($n, $pack, 1, "$n using $pack found") && next;
+    }
+
+    # handle ${varname} in package name
+    if ( $pack =~ s/\$\{\w+\}//) {
+      insert_pkg($n, $pack, 1, "$n using $pack found") && next;
+    }
+
     # else package is unknown
     push @unknown, $n;
   }