Change Ubuntu test platform on master to 18.04.

util/ci/ubuntu-18.04-docker

@@ -1,4 +1,4 @@
-from ubuntu:16.04
+from ubuntu:18.04
 # Travis' ubuntu docker images don't have any package sources enabled by default
 # So start by enabling what we need
 run sed -i"" "s/^# deb-src/deb-src/" /etc/apt/sources.list
@@ -11,9 +11,8 @@ run apt-get update -y
 run DEBIAN_FRONTEND=noninteractive apt-get install -y --no-install-recommends apt-utils
 run DEBIAN_FRONTEND=noninteractive apt-get upgrade -y
 run DEBIAN_FRONTEND=noninteractive apt-get build-dep -y gnucash
-run DEBIAN_FRONTEND=noninteractive apt-get install -y git bash-completion cmake make swig xsltproc libdbd-sqlite3 texinfo ninja-build libboost-all-dev libgtk-3-dev libwebkit2gtk-3.0-dev tzdata
+run DEBIAN_FRONTEND=noninteractive apt-get install -y git bash-completion cmake make swig xsltproc libdbd-sqlite3 texinfo ninja-build libboost-all-dev libgtk-3-dev libwebkit2gtk-4.0-dev tzdata googletest
 run DEBIAN_FRONTEND=noninteractive apt-get --reinstall install -y language-pack-en language-pack-fr
-run git clone https://github.com/google/googletest -b release-1.8.0 gtest
-copy ubuntu-16.04-testscript afterfailure commonbuild /
-run chmod +x /ubuntu-16.04-testscript /afterfailure /commonbuild
-entrypoint /ubuntu-16.04-testscript
+copy ubuntu-18.04-testscript afterfailure commonbuild /
+run chmod +x /ubuntu-18.04-testscript /afterfailure /commonbuild
+entrypoint /ubuntu-18.04-testscript

util/ci/ubuntu-18.04-testscript

@@ -3,8 +3,4 @@
 # -e above so that if any command has an exit code != 0, this script will
 #  exit immediately.
 
-export GTEST_ROOT=/gtest
-export PLATFORM_CMAKE_OPTS="-DALLOW_OLD_GETTEXT=ON"
-echo PLATFORM_CMAKE_OPTS= "$PLATFORM_CMAKE_OPTS"
-
 ../commonbuild