[gtk/macos-ci] ci: Add a macos build

[Matthias Clasen <matthiasc src gnome org>]

commit 55754c1ee4b733598f53753c7d6f2c7d1d2d5c75
Author: Matthias Clasen <mclasen redhat com>
Date:   Sat Jan 2 22:34:52 2021 -0500

    ci: Add a macos build
    
    Most of this is cribbed from glib.

 .gitlab-ci.yml                           | 16 ++++++++++++++++
 .gitlab-ci/show-execution-environment.sh | 11 +++++++++++
 2 files changed, 27 insertions(+)
---
diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 18565b2913..6640e066d7 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -144,6 +144,22 @@ msys2-mingw64:
     MSYSTEM: "MINGW64"
     CHERE_INVOKING: "yes"
 
+macos:
+  stage: build
+  tags:
+    - macos
+  needs: []
+  before_script:
+    - bash .gitlab-ci/show-execution-environment.sh
+    - pip3 install --user meson
+    - pip3 install --user ninja
+    - export PATH=/Users/gitlabrunner/Library/Python/3.7/bin:$PATH
+  script:
+    - meson subprojects update
+    - meson ${COMMON_MESON_FLAGS} ${EXTRA_MESON_FLAGS} ${BACKEND_FLAGS} ${FEATURE_FLAGS}
+            _build
+    - ninja -C _build
+
 .flatpak-defaults:
   image: $FLATPAK_IMAGE
   stage: flatpak
diff --git a/.gitlab-ci/show-execution-environment.sh b/.gitlab-ci/show-execution-environment.sh
new file mode 100755
index 0000000000..0c22651616
--- /dev/null
+++ b/.gitlab-ci/show-execution-environment.sh
@@ -0,0 +1,11 @@
+#!/bin/bash
+
+set -eux -o pipefail
+
+id || :
+capsh --print || :
+env -0 | sort -z | perl -pe 's/\0/\n/g' || :
+setpriv --dump || :
+ulimit -a || :
+cat /proc/self/status || :
+cat /proc/self/mountinfo || :