Use ninja in ci

.ci/install.sh

@@ -5,7 +5,7 @@ set -ex
 if [ $TRAVIS_OS_NAME == osx ]; then
     brew update || true
     brew upgrade boost || true
-    brew install libsodium clang-format
+    brew install libsodium clang-format ninja
     brew tap nlohmann/json
     # the nlohmann install seems to make travis angry 
     # because of the number of log messages

.travis.yml

@@ -20,11 +20,13 @@ matrix:
       env:
         - CXX_VERSION=g++-8
         - CC_VERSION=gcc-8
+        - CMAKE_GENERATOR=Ninja
     - os: linux
       compiler: clang
       env:
         - CXX_VERSION=clang++-6.0
         - CC_VERSION=clang-6.0
+        - CMAKE_GENERATOR=Ninja
         - COVERAGE=ON
 
 install:

Dockerfile

@@ -9,7 +9,7 @@ ENV CMAKE_SHORT_VERSION=3.15
 
 RUN \
     apt-get update -qq && \
-    apt-get install -y --no-install-recommends apt-transport-https software-properties-common curl && \
+    apt-get install -y --no-install-recommends apt-transport-https software-properties-common curl ninja-build && \
     # cmake
     curl https://cmake.org/files/v${CMAKE_SHORT_VERSION}/cmake-${CMAKE_VERSION}-Linux-x86_64.sh -o cmake-install.sh && \
     bash cmake-install.sh --skip-license --prefix=/usr/local && \