[duneproject][Bugfix] Make sure dune_enable_all_packages() can actually be disabled

The shell script logic for switching dune_enable_all_packages() on or
off in duneproject was broken and always turned the feature on, ignoring
the user input.

Fixed by testing for the actual contents of the variable instead of its
length and by converting the contents to lowercase before.

(cherry picked from commit 346657b7)
Signed-off-by: Carsten Gräser <graeser@dune-project.org>

bin/duneproject

@@ -269,6 +269,10 @@ while [ "$DATACORRECT" != "y" -a "$DATACORRECT" != "Y" ]; do
 
 
 
+# canonicalize contents of ENABLE_ALL
+ENABLE_ALL=$(tr '[:upper:]' '[:lower:]' <<< "$ENABLE_ALL")
+
+
 echo
 echo "A sample code $MODULE.cc is generated in the \"$PROJECT\" directory."
 echo "Look at the README and dune.module files there."