[gxml] CI: Updated pre-build for meson

[Daniel Espinosa Ortiz <despinosa src gnome org>]

commit c8b4d582fec6d8b4722efe6731c62371673ab922
Author: Daniel Espinosa <esodan gmail com>
Date:   Fri Mar 2 11:23:11 2018 -0600

    CI: Updated pre-build for meson

 .gitlab-ci.yml | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)
---
diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index fee485f..4333fe4 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -5,8 +5,7 @@ stages:
   - build
 
 before_script:
-  - apt install pip3 libxml2-dev libglib2.0-dev valac
-  - pip3 install meson
+  - apt install libxml2-dev libglib2.0-dev valac meson
 
 build-gxml:
   stage: build