Bump ubuntu version

.gitlab-ci.yml

@@ -43,27 +43,19 @@ build synapse arm64:
 
 .build-linux:
   stage: build
-  image: ubuntu:18.04
+  image: ubuntu:20.04
   services:
     - name: $CI_REGISTRY_IMAGE/synapse-${M_ARCH}:latest
       alias: synapse
   variables:
-    CXX: g++-7
-    CC: gcc-7
     TRAVIS_OS_NAME: linux
   before_script:
     - apt-get update
     - apt-get install -y software-properties-common
     - add-apt-repository ppa:ubuntu-toolchain-r/test -y
-    - apt-get update && apt-get -y install --no-install-recommends ${CXX} ${CC} build-essential ninja-build libssl-dev git ccache curl lcov gcovr
+    - apt-get update && apt-get -y install --no-install-recommends build-essential ninja-build libssl-dev git ccache curl lcov gcovr cmake libgtest-dev
     # need recommended deps for wget
     - apt-get -y install wget
-    - wget https://github.com/Kitware/CMake/releases/download/v3.20.0-rc4/cmake-3.20.0-rc4-linux-${M_ARCH}.sh && sh cmake-3.20.0-rc4-linux-${M_ARCH}.sh  --skip-license  --prefix=/usr/local
-    - /usr/sbin/update-ccache-symlinks
-    - update-alternatives --install /usr/bin/gcc gcc "/usr/bin/${CC}" 10
-    - update-alternatives --install /usr/bin/g++ g++ "/usr/bin/${CXX}" 10
-    - update-alternatives --set gcc "/usr/bin/${CC}"
-    - update-alternatives --set g++ "/usr/bin/${CXX}"
     - rm -rf ../.hunter && mv .hunter ../.hunter || true
   script:
     - curl -s -f -k https://synapse:8008/_matrix/client/versions