Consistently generate build tags metadata

[sigv]

References: cosmos/gaia#2017

What is the purpose of the change

Dockerfile receives a minor tweak for proper output.

BuildTags value is expected as a plain netgo,ledger,muslc string, however the current approach wraps quotes inside of quotes, and the resulting string is 'netgo,ledger,muslc' which gets escaped a few more times (unnecessarily).

Additionally, Makefile receives a minor tweak for everyone who builds directly.

With Make 4.3+, the empty whitespace does not seem to work as originally intended. This causes build tags to be netgo ledger, on Ubuntu 22.04 and other systems that include the newer Make version. The build tags were intended as netgo,ledger which can be observed on Make 4.2 (shipped with Ubuntu 20.04).

This change swaps out the += use in favor of an explicit :=. Reference

Brief Changelog

• Consistently generate build tags metadata, to return a comma-separated list without stray quotes. This affects the output from version CLI subcommand and server info API calls.

Testing and Verifying

This change is a trivial rework / code cleanup without any test coverage.

The difference in build_tags output can be observed:

# pre-built (v14.0.1)
$ osmosisd-14.0.1-linux-amd64 version --long 2>&1 | head -n5
name: osmosis
server_name: osmosisd
version: 14.0.1
commit: 0a4b5bed878af2ea2167749f937e7cdde21f9031
build_tags: '''netgo,ledger,muslc'''

# `docker build -t osmosis .` (PR branch)
$ docker run --rm -it osmosis version --long | head -n5
name: osmosis
server_name: osmosisd
version: ""
commit: ""
build_tags: netgo,ledger,muslc

Documentation and Release Note

• Does this pull request introduce a new feature or user-facing behavior changes? (yes) If someone is actually parsing these programmatically, then it's a user-facing behavior changes.
• Is a relevant changelog entry added to the Unreleased section in CHANGELOG.md? (yes)
• How is the feature or change documented? (not applicable) The behavior change is implementing the originally intended BuildTags behavior by Cosmoshub/Gaia and all derivatives. A changelog warning is in place, but further documentation is not beneficial here.

[p0mvn]

utACK, thank you for the through breakdown and references!