Bug#1119091: qt6-tools: build with default clang/llvm

[Jeremy Bícha <jbicha@debian.org>]

Source: qt6-tools
Version: 6.9.2-2
Tags: patch
X-Debbugs-CC: eltaone@debian.org

Please consider building with the default clang/llvm rather than
manually specifying a version. In my follow-up email, I'm attaching a
patch to do this.

It looks like this was already being done until
https://salsa.debian.org/qt-kde-team/qt6/qt6-tools/-/commit/f3938d78

Please also update qt6-tools to 6.9.3 (or 6.10) since it includes
fixes needed for qt6-tools to build with llvm 21. Ubuntu has already
switched its default llvm to 21 and Debian will follow. (llvm 20 is
being skipped in Debian.)

Thank you,
Jeremy Bícha