Makefile: add copy bor binary to go bin command

[manav2401]

This PR adds a command to copy bor binary from ./build/bin/bor to go bin.

[codecov-commenter]

Codecov Report

Merging #469 (fe48a28) into develop (9dcc993) will decrease coverage by 0.11%.
The diff coverage is n/a.

@@             Coverage Diff             @@
##           develop     #469      +/-   ##
===========================================
- Coverage    56.25%   56.14%   -0.12%     
===========================================
  Files          606      603       -3     
  Lines        69846    69823      -23     
===========================================
- Hits         39294    39202      -92     
- Misses       27169    27216      +47     
- Partials      3383     3405      +22     

Impacted Files	Coverage Δ
eth/downloader/modes.go	17.24% <0.00%> (-6.90%)	⬇️
node/defaults.go	24.13% <0.00%> (-6.90%)	⬇️
rlp/raw.go	79.37% <0.00%> (-5.63%)	⬇️
core/state/trie_prefetcher.go	74.80% <0.00%> (-5.35%)	⬇️
consensus/ethash/algorithm.go	88.81% <0.00%> (-5.27%)	⬇️
eth/downloader/fetchers.go	61.90% <0.00%> (-4.77%)	⬇️
accounts/keystore/watch.go	90.69% <0.00%> (-4.66%)	⬇️
les/utils/exec_queue.go	88.88% <0.00%> (-2.78%)	⬇️
p2p/discover/table.go	82.48% <0.00%> (-2.56%)	⬇️
core/rawdb/freezer_batch.go	77.21% <0.00%> (-2.54%)	⬇️
... and 26 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 9dcc993...fe48a28. Read the comment docs.