message: Upgrade to yaml-cpp to 0.6.1.
diff: set -e
  -# Using a pinned commit rather than release version to avoid taking the Boost
  -# dependency present in last release.
  -COMMIT=e2818c423e5058a02f46ce2e519a82742a8ccac9 # 2017-07-25
  +VERSION=0.6.1
  -git clone https://github.com/jbeder/yaml-cpp
  -cd yaml-cpp
  -git reset --hard "$COMMIT"
  +wget -O yaml-cpp-"$VERSION".tar.gz https://github.com/jbeder/yaml-cpp/archive/yaml-cpp-"$VERSION".tar.gz
  +tar xf yaml-cpp-"$VERSION".tar.gz
  +cd yaml-cpp-yaml-cpp-"$VERSION"
  cmake -DCMAKE_INSTALL_PREFIX:PATH="$THIRDPARTY_BUILD" \
  -DCMAKE_CXX_FLAGS:STRING="${CXXFLAGS} ${CPPFLAGS}" \
  -DCMAKE_C_FLAGS:STRING="${CFLAGS} ${CPPFLAGS}" \
  