message: add LDFLAGS for clang
diff: @@ -80,6 +80,7 @@ matrix:
  #build settings
  - build_type=Release
  - CXX_STANDARD=17
  + - LDFLAGS="-fuse-ld=lld"
  addons:
  apt:
  packages: ['clang-10', 'clang++-10', 'clang-format-10', 'clang-tools-9', 'cmake']
  