Build fails on debian-10

[MaoZiming]

Describe the bug
Build fails with

In member function ‘virtual void folly::AsyncSocket::writeChain(folly::AsyncWriter::WriteCallback*, std::unique_ptr<folly::IOBuf>&&, folly::WriteFlags)’:
/home/CacheLib/cachelib/external/folly/folly/io/async/AsyncSocket.cpp:1733:15: error: ‘BOOST_PP_IF’ was not declared in this scope
     iovec vec[BOOST_PP_IF(FOLLY_HAVE_VLA_01, count, kSmallIoVecSize)];
               ^~~~~~~~~~~
/home/CacheLib/cachelib/external/folly/folly/io/async/AsyncSocket.cpp:1733:15: note: suggested alternative: ‘BOOST_PP_IIF’
     iovec vec[BOOST_PP_IF(FOLLY_HAVE_VLA_01, count, kSmallIoVecSize)];
               ^~~~~~~~~~~
               BOOST_PP_IIF
/home/CacheLib/cachelib/external/folly/folly/io/async/AsyncSocket.cpp:1736:30: error: ‘vec’ was not declared in this scope
     writeChainImpl(callback, vec, count, std::move(buf), flags);

To Reproduce
Steps to reproduce the behavior:
./contrib/build.sh -d -j -v

[therealgymmy]

yeah this is a known issue. You can try a platform such as centos 9.0 for now.

We need to debug further. Our OSS builds have been very fragile in the last month or so. Multiple dependencies broke one after another. Details in #310

[therealgymmy]

should be fixed by now