I worked around it by just adding the missing include folders within the build directories with this
export CPLUS_INCLUDE_PATH="/home/eynhaender/development/libbitcoin/build/release_static/include/bitcoin/network/ssl:$CPLUS_INCLUDE_PATH"
export CPATH="/home/eynhaender/development/libbitcoin/build/release_static/include/bitcoin/network/ssl:$CPATH"