Fix the CI build

.gitlab-ci.yml

@@ -2,6 +2,11 @@ image: golang:1.10
 
 build:
   script:
+    - apt-get update && apt-get install -q -yy libx11-dev libxcursor-dev mesa-common-dev libxrandr-dev libxinerama-dev libgl1-mesa-dev libxi-dev
+    - export GOPATH=`pwd`/.GOPATH
+    - mkdir -p $GOPATH/src/ur.gs
+    - ln -s `pwd` $GOPATH/src/ur.gs/ordoor
     - make all
+    - rm -rf .GOPATH
   artifacts:
     untracked: true

README.md

@@ -22,6 +22,14 @@ $ go version
 go version go1.10 linux/amd64
 ```
 
+In addition, you'll also need the following packages installed, at least in
+Debian:
+
+```
+apt-get install libx11-dev libxcursor-dev mesa-common-dev libxrandr-dev \
+  libxinerama-dev libgl1-mesa-dev libxi-dev
+```
+
 Clone the source tree to `$GOPATH/src/ur.gs/ordoor`. You can then run
 `make all` to get the binaries that exist at present.