Reduce the size of the commands needed to make documentation
Reduce the size of the commands needed to make documentation

It failed to run on windows due to a limitations of the length
of the command line with cmd.exe.

This patch splits all commands into separate lines.
On windows, it will additionally split each environment setting
to a separate line.

Task-number: QTBUG-25758
Change-Id: I164a5d3b09b400259b3d20d3a565265ae4e4f975
Reviewed-by: Martin Smith <a8cc6484db2755056ccf1c457da8ca771f895dea@digia.com>
Reviewed-by: Oswald Buddenhagen <6a8868beda3e139b5ac22b2534a23d3e6ba81819@digia.com>

kobolabs/qtdoc,kobolabs/qtdoc,kobolabs/qtdoc,kobolabs/qtdoc