message: Snap: Reduce build parallelism
  Snapcraft dockerized builds seem to have a problem with performing them.
diff: @@ -129,8 +129,7 @@ parts:
  CPPFLAGS="-I${SNAPCRAFT_STAGE}/include -I${SNAPCRAFT_PART_INSTALL}/../build/deps/json/src" \
  LDFLAGS="-Wl,--copy-dt-needed-entries -L${SNAPCRAFT_STAGE}/lib" \
  PKG_CONFIG_PATH="${SNAPCRAFT_STAGE}"/lib/pkgconfig
  - make \
  - --jobs=$(nproc)
  + make -j2
  make prefix="${SNAPCRAFT_PART_INSTALL}" install-strip
  sed \
  @@ -207,8 +206,7 @@ parts:
  --prefix="${SNAPCRAFT_PART_INSTALL}" \
  --with-libraries=iostreams,regex,system,thread,random,filesystem,chrono,atomic,date_time \
  --with-icu=/usr
  - ./b2 install \
  - -j $(nproc) \
  + ./b2 install -j4 \
  --build-type=minimal \
  --layout=system \
  link=static \
  @@ -311,8 +309,7 @@ parts:
  CC=gcc-6 \
  CPP=cpp-6 \
  CXX=g++-6
  - make \
  - --jobs=$(nproc)
  + make -j4
  make prefix="${SNAPCRAFT_PART_INSTALL}" install
  stage-packages:
  