Qt: add version 6.8.0

[tobiaskhuber]

Summary

Added Qt version 6.8.0

Motivation

There are several new features and bugfixes in Qt 6.8.
https://code.qt.io/cgit/qt/qtreleasenotes.git/about/qt/6.8.0/release-note.md

Details

Qt 6.8.0 has been added to the Qt recipe.

---

• Read the contributing guidelines
• Checked that this PR is not a duplicate: list of PRs by recipe
• Tested locally with at least one configuration using a recent version of Conan

[CLAassistant]

All committers have signed the CLA.

[valgur]

It's currently missing the patches that have been applied to the previous versions.

[tobiaskhuber]

Thanks for the review. I made the requested changes.

[valgur]

Thanks!

[valgur]

Probably needs these changes as well:

• https://github.com/valgur/conan-center-index/blob/17a0ddf60ac30cbea0f6bf61e8492828cc6f77d0/recipes/qt/6.x.x/conanfile.py#L761-L766
• https://github.com/valgur/conan-center-index/blob/17a0ddf60ac30cbea0f6bf61e8492828cc6f77d0/recipes/qt/6.x.x/conanfile.py#L1183-L1201

[valgur]

Qt 6.8.0 now also refuses to build when using libstdc++ without GNU extensions being enabled in the cppstd:

• qt/qtbase@7805b3c
• https://github.com/qt/qtbase/blob/v6.8.0/src/corelib/global/qtypes.cpp#L506-L511

The check for QT_SUPPORTS_INT128 only takes place during the building of Qt itself and not in the public headers, though. Maybe the GNU extensions could be enabled automatically by the recipe in the CMakeToolchain?

The alternative would be to validate this case in validate_build() and possibly also expose an enable_int128 option if the user is ok with disabling it to keep the non-GNU cppstd.

@jcar87 What do you think?

[valgur]

Suggested change

	"patch_file": "patches/c72097e_6.8.0.diff"
	"patch_file": "patches/c72097e_6.6.0.diff"

I think you can keep using the existing patch?

[tobiaskhuber]

I had to change it because the file that this patch applies to has changed between 6.7 and 6.8

[tobiaskhuber]

These changes also seem to be necessary for qt 6.8