libgo: add Debugging section to README

Change-Id: I017778465271e118f4fa84a26fe91c28e0ca036b
Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/176001
Reviewed-by: Cherry Zhang <cherryyz@google.com>
Reviewed-by: Than McIntosh <thanm@google.com>
1 file changed