feat: Add Ninja build. (#2931)

Author: remyabel

ci/kokoro/docker/Dockerfile.ubuntu

@@ -36,6 +36,7 @@ RUN apt update && \
         libtool \
         lsb-release \
         make \
+        ninja-build \
         pkg-config \
         python-pip \
         shellcheck \

ci/kokoro/docker/build-in-docker-cmake.sh

@@ -68,6 +68,10 @@ if [[ "${USE_LIBCXX:-}" == "yes" ]]; then
   cmake_extra_flags+=( "-DGOOGLE_CLOUD_CPP_USE_LIBCXX=ON" )
 fi
 
+if [[ "${USE_NINJA:-}" == "yes" ]]; then
+  cmake_extra_flags+=( "-GNinja" )
+fi
+
 # We use parameter expansion for ${cmake_extra_flags} because set -u doesn't
 # like empty arrays on older versions of Bash (which some of our builds use).
 # The expression ${parameter+word} will expand word only if parameter is not

ci/kokoro/docker/build.sh

@@ -74,6 +74,9 @@ elif [[ "${BUILD_NAME}" = "cmake-super" ]]; then
   # what spanner does where RUN_INTEGRATION_TESTS is explicitly set to yes.
   export RUN_INTEGRATION_TESTS="no"
   in_docker_script="ci/kokoro/docker/build-in-docker-cmake.sh"
+elif [[ "${BUILD_NAME}" = "ninja" ]]; then
+  # Compiling with Ninja can catch bugs that may not be caught using Make.
+  export USE_NINJA=yes
 elif [[ "${BUILD_NAME}" = "gcc-9" ]]; then
   # Compile under fedora:30. This distro uses gcc-9.
   export DISTRO=fedora
@@ -221,6 +224,9 @@ docker_flags=(
     # If set, enable using libc++ with CMake.
     "--env" "USE_LIBCXX=${USE_LIBCXX:-}"
 
+    # If set, enable the Ninja generator with CMake.
+    "--env" "USE_NINJA=${USE_NINJA:-}"
+
     # If set, use Clang's static analyzer. Currently there is no build that
     # uses this feature, it may have rotten.
     "--env" "SCAN_BUILD=${SCAN_BUILD:-}"