Fix invalid path to the qt-cmake.bat when calling qt-internal-configure-tests.bat

Since qt-internal-configure-tests.bat is located in the same folder as
qt-cmake.bat the relative_path_from_libexec_dir_to_bin_dir is empty.

Passing doubled backslash in the windows path causes an issue for the
cmd.exe batch interpreter. Extra backslashes are treated by %~dp0 as a
start of the relative path. The following error appears:

   Could not find toolchain file:
     ...\install\bin\..\/../lib/cmake/Qt6/qt.toolchain.cmake

This appends an extra backslash to relative_bin_dir only if
relative_path_from_libexec_dir_to_bin_dir is not empty.

Change-Id: Id2fd6c5fa9d73060350f298262c6e93a4887eeb3
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Alexandru Croitor <alexandru.croitor@qt.io>

0 files changed, 0 insertions, 0 deletions