xserver_xorg-server: Fix race condition when installing man pages
Reproduced the bug using BR2_JLEVEL=16
Fixes race condition by disabling parallel make in man/
http://autobuild.buildroot.net/results/11e/
11ece737078ca8da2fee4249432148675b4e630e/
http://autobuild.buildroot.net/results/a95/
a952932b832ee3296d6c225c7a9df408ca3eef9f/
Signed-off-by: Bernd Kuhls <bernd.kuhls@t-online.de>
Reviewed-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>