In CI, build from a copy of the source tree

.github/workflows/ci-conan.yml

@@ -32,7 +32,8 @@ jobs:
           cat <<'EOF' >/tmp/osp-builder-docker/entrypoint.sh
           #!/bin/bash -v
           set -eu
-          cd /mnt/source
+          cp -r /mnt/source /root/build
+          cd /root/build
           conan remote add osp https://osp.jfrog.io/artifactory/api/conan/conan-local --force
           conan create -s build_type=${{ matrix.build_type }} -s compiler.libcxx=libstdc++11 -o "libcosim/*:${{ matrix.option_shared }}" -b missing .
           conan upload --confirm --remote=osp 'fmilibrary*'
@@ -41,7 +42,7 @@ jobs:
       - name: Build Docker image
         run: docker build -t osp-builder /tmp/osp-builder-docker/
       - name: Build FMI Library
-        run: docker run --rm --env GITHUB_REF="$GITHUB_REF" -v $(pwd):/mnt/source:rw osp-builder
+        run: docker run --rm --env GITHUB_REF="$GITHUB_REF" -v $(pwd):/mnt/source:ro osp-builder
 
   conan-on-windows:
     name: Conan