CMake: Enable CXX compiler for tests only

[gadoofou87-zz]

Fixes #109

[Mizux]

LGTM, just need to wait for CI to finish

[gadoofou87-zz]

I think the build error is due to this commit google/googletest@23b2a3b

[Mizux]

I think we should set properties on source files to set LANGUAGE to CXX
ref: https://cmake.org/cmake/help/latest/prop_sf/LANGUAGE.html

[Mizux]

you should try to move it just after if(BUILD_TESTING) line 162 so googletest is build with support enabled

[gadoofou87-zz]

Almost fixed! :)

[Mizux]

Last remaining issue is ci setup bug (no ninja on ppc64) -> unrelated to this PR

[Mizux]

BTW I was not able to reproduce it using a docker
ci/Dockerfile:

# Create a virtual environment with all tools installed
# ref: https://hub.docker.com/_/ubuntu
FROM ubuntu:rolling AS env
LABEL maintainer="mizux.dev@gmail.com"
# Install system build dependencies
RUN apt-get update -qq \
&& apt-get install -yq git wget curl libssl-dev build-essential ninja-build \
&& apt-get install -yq python3-dev python3-pip \
&& apt-get clean \
&& rm -rf /var/lib/apt/lists/* /tmp/* /var/tmp/*
# Install CMake 3.16.4
RUN wget "https://cmake.org/files/v3.16/cmake-3.16.4-Linux-x86_64.sh" \
&& chmod a+x cmake-3.16.4-Linux-x86_64.sh \
&& ./cmake-3.16.4-Linux-x86_64.sh --prefix=/usr/local/ --skip-license \
&& rm cmake-3.16.4-Linux-x86_64.sh
CMD [ "/bin/bash" ]

# Create lib directory
WORKDIR /home/lib
# Bundle lib source
COPY . .

FROM env as build
RUN cmake -S. -Bbuild -DCMAKE_BUILD_TYPE=Debug -DBUILD_TESTING=ON -GNinja
#RUN cmake -S. -Bbuild -DBUILD_TESTING=ON
RUN cmake --build build

FROM build as test
RUN cmake --build build --target test

docker build -t cpu_feature  -f ci/Dockerfile  .

[Mizux]

FYI last master build was one month ago, without ppc64 jobs
see: #329

I've just triggered a build master: #334

EDIT: after inspection it seems that previously, ppc64 runner was in reality amd64 runner -_-