gtk3: partially revert d0aca00

[cooljeanius]

Closes: https://trac.macports.org/ticket/70274

Description

PR #23864 added 2 active variants checks to gtk3 on glib2, but really only one of them was needed. This PR removes the unnecessary one.

Type(s)

• bugfix
• enhancement
• security fix

Tested on

macOS 11.7.10 20G1427 x86_64
Xcode 13.2.1 13C100

Verification

Have you

• followed our Commit Message Guidelines?
• squashed and minimized your commits?
• checked that there aren't other open pull requests for the same change?
• referenced existing tickets on Trac with full URL in commit message?
• checked your Portfile with port lint --nitpick? (it mentions "Warning: Unnecessary platforms line as darwin is the default" in the output, but I don't think that I should fix that here, as that seems off-topic, and it was already there)
• tried existing tests with sudo port test? (it looks like I'll need to review the libepoxy active variants check, too...)
• tried a full install with sudo port -vst install?
• tested basic functionality of all binary files?
• checked that the Portfile's most important variants haven't been broken?

[macportsbot]

Notifying maintainers:
@mascguy for port gtk3.

[cooljeanius]

oh wait, I forgot I'd have to do this for gtk3-devel, too; let me fix that...

[cooljeanius]

So I'm trying to see if I can remove the active_variants check on libepoxy, too, but now I'm running into 67675 again; aaaaah... the hack I discovered there of adding -Wl,-F/System/Library/Frameworks/ to configure.ldflags doesn't really seem appropriate for this PR...

[cooljeanius]

So I'm trying to see if I can remove the active_variants check on libepoxy, too, but now I'm running into 67675 again; aaaaah... the hack I discovered there of adding -Wl,-F/System/Library/Frameworks/ to configure.ldflags doesn't really seem appropriate for this PR...

Could I get some feedback as to whether or not I should add that part here, too? It'd let me test properly, but also it's kind of a workaround...