nixos: fix two pipefail problems

It failed since 3c6efec2c09, i.e. #4453.
Now it should "work" the same as before.
cairo: major update 1.12.* -> 1.14.0

ABI diff only suggest that one enum value got updated,
which should be fine for us.
http://upstream-tracker.org/compat_reports/cairo/1.12.16_to_1.14.0/abi_compat_report.html#Low_Risk_Problems
gtk2: bugfix update
glib: feature update 2.40.* -> 2.42.0

http://upstream-tracker.org/ looks good enough, and so do the NEWS.
mesa: bugfix update

I'm still having some problems with 10.3.1 compilation.
xorg: updates some modules; mostly minor changes
libdrm: update
libiconv: update to 1.14 (close #4419)
gstreamer-1: maintenance updates of all
libevdev: small update