[gnome-calculator] build: Update required meson version

[Robert Roth <robertroth src gnome org>]

commit 9c94cc009dac8802e5b3b9197ded9e052b8d1fcc
Author: Diego Escalante Urrelo <diegoe gnome org>
Date:   Sat Aug 31 08:13:51 2019 -0500

    build: Update required meson version
    
    Also update gitlab-ci to install meson from pip3
    
    Closes: https://gitlab.gnome.org/GNOME/gnome-calculator/issues/127

 .gitlab-ci.yml | 4 +++-
 meson.build    | 2 +-
 2 files changed, 4 insertions(+), 2 deletions(-)
---
diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 6bfc5fa4..a397785c 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -2,7 +2,9 @@
   image: ubuntu:rolling
   before_script:
     - apt-get update
-    - apt-get install -q -y --no-install-recommends meson valac gcc gettext itstool libgtk-3-dev 
libgtksourceview-4-dev libmpc-dev libmpfr-dev libsoup2.4-dev libxml2-dev libgee-0.8-dev
+    - apt-get install -q -y --no-install-recommends valac gcc gettext itstool libgtk-3-dev 
libgtksourceview-4-dev libmpc-dev libmpfr-dev libsoup2.4-dev libxml2-dev libgee-0.8-dev libvala-0.44 
python3-pip ninja-build
+    - pip3 install --upgrade setuptools
+    - pip3 install --no-cache-dir meson>=0.50.0
 
 .before_script_template: &fedora_before_script
   image: fedora:latest
diff --git a/meson.build b/meson.build
index d2d88cb0..a7b175e3 100644
--- a/meson.build
+++ b/meson.build
@@ -1,6 +1,6 @@
 project('gnome-calculator', ['c', 'vala'],
   version: '3.34.0',
-  meson_version: '>= 0.42',
+  meson_version: '>= 0.50.0',
   license: 'GPLv3+',
 )