The BUILD_DIR on Appveyor has different names sometimes, use a consistent
directory name to avoid build failures.
Signed-off-by: Damian Jarek <damian.jarek93@gmail.com>
close#1558
- Parallelize submodule clone.
- Do a shallow submodule clone.
- Move submodule update code to a script.
- Build with BOOST_BEAST_USE_STD_STRING_VIEW on msvc
Signed-off-by: Damian Jarek <damian.jarek93@gmail.com>