devel/valgrind-devel: Use option helpers and update formatting

[jrm]

Summary

This is a separate commit from the update discussed in D37197. It modernizes the Makefile a bit by using OPTION helpers and standardizes the formatting using portclippy/portfmt.

Approved by: [e-mail] (maintainer)

Test Plan

poudriere testport with all options on and off build successfully

[jrm]

Show the revision relative to the update discussed in D37197.

Phabricator messes with the whitespace in the default view. The raw diff might be easier to inspect.

[jrm]

Also, if you are good with these changes, I can do the same for devel/valgrind.

[pjfloyd_wanadoo.fr]

In D37201#844432, @jrm wrote:

Also, if you are good with these changes, I can do the same for devel/valgrind.

No thanks. My current policy is for devel/valgrind to track official releases and for devel/valgrond-devel to have occasional bugfixes between official releases (which are normally only twice a year).

[jrm]

To be clear, I'm just referring to the style changes mostly to conform to Chapter 15. Order of Variables in Port Makefiles and a few other style issues. It's kind of like style(9) for ports. No problem if you prefer to leave things as is, but could you clarify?

[pjfloyd_wanadoo.fr]

In D37201#844760, @jrm wrote:

To be clear, I'm just referring to the style changes mostly to conform to Chapter 15. Order of Variables in Port Makefiles and a few other style issues. It's kind of like style(9) for ports. No problem if you prefer to leave things as is, but could you clarify?

My mistake, I hadn't looked at the change. Yes, that's fine by me.