Add Drone support

.drone/drone.sh

@@ -0,0 +1,24 @@
+#!/bin/bash
+
+# Copyright 2023 Christian Mazakas
+# Distributed under the Boost Software License, Version 1.0.
+# https://www.boost.org/LICENSE_1_0.txt
+
+set -ex
+export PATH=~/.local/bin:/usr/local/bin:$PATH
+
+DRONE_BUILD_DIR=$(pwd)
+
+BOOST_BRANCH=develop
+if [ "$DRONE_BRANCH" = "master" ]; then BOOST_BRANCH=master; fi
+
+cd ..
+git clone -b $BOOST_BRANCH --depth 1 https://github.com/boostorg/boost.git boost-root
+cd boost-root
+git submodule update --init tools/boostdep
+python tools/boostdep/depinst/depinst.py config
+./bootstrap.sh
+./b2 -d0 headers
+
+echo 'using asciidoctor : "/usr/bin/asciidoctor" ;' > ~/user-config.jam
+./b2 $DRONE_BUILD_DIR