ci: implement a sensible travis + docker setup for automated builds

The Dockerfile was rewritten and moved to a separete repository
for doing automated builds on docker hub
-> https://github.com/gkiagia/pipewire_build_environment

.travis.yml

@@ -1,29 +1,22 @@
 sudo: required
-dist: trusty
-language: generic
+language: minimal
 services:
   - docker
-cache:
-  - bundler: true
-  - directories:
-    - $HOME/.docker
-  - ccache
-  - pip
-before_cache:
-  - >
-    mkdir -p $HOME/.docker && docker images -a --filter='dangling=false' --format '{{.Repository}}:{{.Tag}} {{.ID}}'
-    | xargs -n 2 -t sh -c 'test -e $HOME/.docker/$1.tar.gz || docker save $0 | gzip -2 > $HOME/.docker/$1.tar.gz'
-branches:
-  only:
-    - travis-ci
-    - work
 addons:
   apt:
     packages:
       - docker-ce
 before_install:
-  - chmod +x meson.sh
-  - docker build -t build .
-  - docker ps -a
-after_success:
-  - docker --version
+  - docker pull gkiagia/pipewire_build_environment:latest
+script:
+  - >
+    docker run -it --rm -v $PWD:/workdir gkiagia/pipewire_build_environment:latest bash -c
+    'cd /workdir && ./autogen.sh \
+      -Ddocs=true \
+      -Daudiomixer=true \
+      -Daudiotestsrc=true \
+      -Dffmpeg=true \
+      -Dtest=true \
+      -Dvideotestsrc=true \
+      -Dvolume=true \
+    && make && make test'