Add Drone support

.drone.jsonnet

@@ -0,0 +1,51 @@
+# Copyright 2023 Christian Mazakas
+# Distributed under the Boost Software License, Version 1.0.
+# https://www.boost.org/LICENSE_1_0.txt
+
+local triggers =
+{
+    branch: [ "master", "develop", "feature/*", "bugfix/*", "fix/*", "pr/*", "base-template" ]
+};
+
+local linux_pipeline(name, image, environment, packages = "", sources = [], arch = "amd64") =
+{
+    name: name,
+    kind: "pipeline",
+    type: "docker",
+    trigger: triggers,
+    platform:
+    {
+        os: "linux",
+        arch: arch
+    },
+    steps:
+    [
+        {
+            name: "everything",
+            image: image,
+            environment: environment,
+            commands:
+            [
+                'set -e',
+                'uname -a',
+                'wget -O - https://apt.llvm.org/llvm-snapshot.gpg.key | apt-key add -',
+            ] +
+            (if sources != [] then [ ('apt-add-repository "' + source + '"') for source in sources ] else []) +
+            (if packages != "" then [ 'apt-get update', 'apt-get -y install ' + packages ] else []) +
+            [
+                './.drone/drone.sh',
+            ]
+        }
+    ]
+};
+
+[
+
+    linux_pipeline(
+        "Linux 22.04 GCC 11* 32/64",
+        "cppalliance/droneubuntu2204:1",
+        {},
+        "asciidoctor"
+    ),
+
+]

.drone/drone.sh

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+#!/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