Switched to Ubuntu 16.04 for package generation.

The builds on 14.04 were not usable on 14.04, 16.04 and 18.04.

.drone.yml

@@ -1,6 +1,6 @@
 pipeline:
   build_package:
-    image: ubuntu:trusty
+    image: ubuntu:xenial
     pull: true
     when:
       event: tag
@@ -10,11 +10,7 @@ pipeline:
       - CXXFLAGS=-pipe -O2
     commands:
       - rm /etc/apt/apt.conf.d/docker-clean
-      - echo "deb http://ppa.launchpad.net/ubuntu-toolchain-r/test/ubuntu trusty main" >> /etc/apt/sources.list.d/ubuntu-toolchain-r.list
-      - gpg --keyserver hkp://keyserver.ubuntu.com --recv-keys 0x60c317803a41ba51845e371a1e9377a2ba9ef27f
-      - gpg --armor --export 0x60c317803a41ba51845e371a1e9377a2ba9ef27f | apt-key add -
-      - apt-get update -q
-      - apt-get install -qy g++-5 cmake3 pkg-config
+      - apt-get install -qy g++-5 cmake pkg-config
       - apt-get install -qy libcrypto++-dev libmagick++-dev libxdg-basedir-dev
       - apt-get install -qy dpkg-dev d-shlibs rpm file wget
       - gpg --import /var/autosign_gpg.key

README.md

@@ -80,7 +80,7 @@ formats:
 * rpm
 * tar.gz
 
-They are generated on Ubuntu Trusty 64 bit and signed with my
+They are generated on Ubuntu 16.04 64 bit and signed with my
 [automatic signing key](https://tastytea.de/tastytea_autosign.asc).
 
 ### From source