+ add script for getting net length from a def file (#306)

* + add script for getting net length in a def file
+ add net length report for caravel

* regenerate reports due to bad lef path in the previous one

scripts/get_net_length.bash

@@ -0,0 +1,29 @@
+#!/bin/env bash
+
+# usage get_net_length.bash merged.lef design.def wire_length.txt
+set -u
+{
+    openroad -exit -no_splash <<EOF
+read_lef $1
+read_def $2
+variable odb_block [[[::ord::get_db] getChip] getBlock]
+set odb_nets [odb::dbBlock_getNets \$::odb_block]
+set fp [open "$3" w]
+foreach net \$odb_nets {
+    set net_name [odb::dbNet_getName \$net]
+    set wire [odb::dbNet_getWire \$net]
+    if {\$wire != "NULL"} {
+        set wire_length [odb::dbWire_getLength \$wire]
+        set wire_length [expr \$wire_length / 1000.0]
+        puts \$fp "\$net_name \$wire_length"
+    }
+}
+close \$fp
+EOF
+} > $(dirname $3)/get_net_length-openroad.log
+
+filename=$(basename $3)
+filename_no_ext="${filename%%.*}"
+sort_file_path="$(dirname $3)/${filename_no_ext}-sorted.txt"
+cat $3 | sort -k 2 -n | column -t > $sort_file_path
+echo "wrote to $sort_file_path"