nektarpp: update to 5.7.0

[mdave]

Description

Updates nektarpp to 5.7.0.

Type(s)

• bugfix
• enhancement
• security fix

Tested on

macOS 15.1 24B83 arm64
Xcode 16.1 16B40

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?
• tried existing tests with sudo port test?
• 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?

[reneeotten]

@mdave build fails everywhere - please investigate

[mdave]

@reneeotten Thanks. Had a quick look, the macos-15 build fails on building opencascade; macos-13/14 are a bit strange, they get to a linker step and then fail with no error message. Not sure if there's some resource limit that is being hit there, will continue to investigate.