net-mgmt/prometheus: Update to 1.6.0

[ler]

Summary

patch file to update prometheus port to v1.6.0, and some port/packaging improvements

Details of changes in this release are available here: https://github.com/prometheus/prometheus/releases/tag/v1.6.0

PR: 218737
Submitted by: [e-mail] (maintainer)
Approved by: (adamw|rene) (mentor)

Test Plan

poudriere (ok on 12)
poudriere testport results:

10.3-RELEASE-p18 amd64 pass
11.0-RELEASE-p9 amd64 pass

[ler]

Fix a portlint error (tab<->space)

[swills]

net-mgmt/prometheus/Makefile

23–24

Stripping does not break Go binaries, see:

https://honnef.co/posts/2016/10/go-and-strip/

28

Specifying it as "unknown" seems odd, can we find what rev it actually is and specify that? Also, for the branch, builduser and builddate, see if you can find what upstream used for their release build and use that if possible. Not that we want to pretend to be upstreams binary, but just to have a value other than "unknown" and sane. Does this fail to build without some sort of value specified?

[ler]

updated to 1.6.1, removed STRIP=, removed unknown's.

[adamw]

Nicely done, Larry!