configure: Don't escape backslashes in passed configure arguments

It broke drive-less (no C:\ prefix) paths passed to configure.

Invoking configure on Windows with the following args
  qtbase/configure --
 -DCMAKE_INSTALL_PREFIX=\Users\qt\work\install

called CMake with
 -DCMAKE_INSTALL_PREFIX=\\Users\\qt\\work\\install

saying
 Qt will be installed into '//Users/qt/work/install'

and while the build succeeded, installation would fail with

  CMake Error at cmake_install.cmake:41 (file):
    file cannot create directory:
    //Users/qt/work/install/lib/cmake/Qt6BuildInternals.  Maybe need
    administrative privileges.

Note the double slash in the beginning is likely interpreted as a
Windows share URI / UNC path.

The same would happen when passing -prefix '\Users\qt\work\install'

As a reminder, we want to support drive-less prefix paths because
that's what Qt's Coin CI uses passes to ensure DESTDIR installation
works correctly.

Amends cb7f4030bc89471aa6489be60ac1c728a3dfd06b

Pick-to: 6.2 6.3
Fixes: QTBUG-94366
Change-Id: I9267b6f784babfbdaeafc65267ba96c75fa24112
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Alexey Edelev <alexey.edelev@qt.io>

0 files changed, 0 insertions, 0 deletions