Build issues with symlinks

In Homebrew (an open source distribution for macOS users) we have to build Qt in a path that contains symlinks (because Apple and cmake currently make it really hard to do anything else). This bug is a follow-up to https://bugreports.qt.io/browse/QTBUG-113295

This generally builds fine, but we sometime find out issues because it is not a generally tested configuration: but the Qt project is really nice and fixes the issues we report, when we report them Thank you!

One of the issues we have in the past, and for which we are carrying a patch, but which we forgot to report to you, is in qtwebengine. It is currently broken in a build with symlinked path, and it started with Qt 6.2.0 (it was working before). We actually have a fix for that:

On the cmake side, in each of these files:

      qtwebengine/cmake/Gn.cmake
      qtwebengine/cmake/Functions.cmake
      qtwebengine/src/core/api/CMakeLists.txt
      qtwebengine/src/CMakeLists.txt
      qtwebengine/src/gn/CMakeLists.txt
      qtwebengine/src/process/CMakeLists.txt

we replace REALPATH with ABSOLUTE.

Then in:

qtwebengine/src/3rdparty/gn/src/base/files/file_util_posix.cc

we replace

FilePath(full_path)

with

FilePath(input)

I hope the patches are general enough (or can be made general enough) that it can be fixed into the main Qt repo!