build: Set -trimpath for go build
Created by: keegancsmith
This helps make builds more deterministic as well as easier to link pprof to local source files. Added in go1.13. Description of trimpath below:
remove all file system paths from the resulting executable. Instead of absolute file system paths, the recorded file names will begin with either "go" (for the standard library), or a module path@version (when using modules), or a plain import path (when using GOPATH).
Test plan: CI