Update shell code

Now it (mostly) passes shellcheck and is formatted with shfmt.

framework/shims/node

@@ -4,12 +4,13 @@
 
 set -eu
 
-export DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"
+node_shim_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+export node_shim_DIR
 
-source "$DIR/../versions"
+source "$node_shim_DIR"/../versions
 
-node_bin="$DIR/../../$nodejs_bin_dir/node"
+source "$node_shim_DIR"/node.common
+
+node_bin="$node_shim_DIR/../../$nodejs_binary_dir/node"
 
 exec "$node_bin" "$@"
-
-