AVX2: how to detect?

[Thomas Klausner <wiz%NetBSD.org@localhost>]

Hi!

Some package behave differently if they find AVX2 support in the CPU.

For example:

http://www.ki.nu/pkgsrc/reports/current/NetBSD-9.0/20230814.0649/qt6-qt3d-6.5.2/install.log

=> Checking file-check results for qt6-qt3d-6.5.2
ERROR: ************************************************************
ERROR: The following files are in the PLIST but not in /tmp/graphics/qt6-qt3d/work/.destdir/usr/pkg:
ERROR:         /tmp/graphics/qt6-qt3d/work/.destdir/usr/pkg/qt6/include/Qt3DCore/6.5.2/Qt3DCore/private/matrix4x4_avx2_p.h

Does anyone have an idea how to detect this properly for pkgsrc?
 Thomas