qt6 configure: Search moc also in $QT6DIR/bin

If QT6DIR is set, search for moc (Qt's meta object compiler)
also in the "bin" subdirectory, which is where moc is placed
in Qt installations on Windows, unlike the "libexec" subdir
that (typically) gets used on Linux.

Only use the $QT6DIR subdirectories when the QT6DIR variable
is actually set (i.e. don't add /bin or /libexec to the search path
otherwise, which was previously the case for /libexec, though
other than /bin that doesn't typically exist on a Linux
system) and give the $QT6DIR subdirectories the highest
preference by putting them first.

This prepares for the pending Gerrit change [1] to
support the qt6 vcl plugin also on Windows.

[1] https://gerrit.libreoffice.org/c/core/+/199615

Change-Id: I38d5f7116368e10b12a242bd1ad122a5f4a82736
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/202905
Tested-by: Jenkins
Reviewed-by: Hossein <hossein@libreoffice.org>

0 files changed, 0 insertions, 0 deletions