Fix compilation

```
building '/nix/store/7n2cag47gl93wp3f0mv7fiq3dybq2a6l-wkhtmltopdf-0.12.5.drv'...
unpacking sources
unpacking source archive /nix/store/lv2zcapqqn1kjlc616ljap1ddlc2lvx8-source
source root is source
patching sources
configuring
Info: creating stash file /tmp/nix-build-wkhtmltopdf-0.12.5.drv-0/source/.qmake.stash
building
build flags: -j4 -l4 SHELL=/nix/store/i82x3x0yiijkgyqkzh8ni87gspas0f48-bash-4.4-p23/bin/bash
cd src/lib/ && ( test -e Makefile || /nix/store/334ck8czp3jhfy0ppy55sb6dxf7yxsdv-qtbase-5.12.0-dev/bin/qmake -o Makefile /tmp/nix-build-wkhtmltopdf-0.12.5.drv-0/source/src/lib/lib.pro INSTALLBASE=/nix/store/rc8z502xa3w0n2qm2vmr5d3l73v1lyyd-wkhtmltopdf-0.12.5 ) && make -f Makefile
Project ERROR: Unknown module(s) in QT: xmlpatterns
make: *** [Makefile:47: sub-src-lib-make_first-ordered] Error 3
builder for '/nix/store/7n2cag47gl93wp3f0mv7fiq3dybq2a6l-wkhtmltopdf-0.12.5.drv' failed with exit code 2
```