docs: reconfigure libbpf documentation syncing

This adds documentation files, including ones for autogenerating API
documentation based on code comments in the source code that's pulled
in via the mirror.

Signed-off-by: Grant Seltzer <grantseltzer@gmail.com>

docs/conf.py

@@ -0,0 +1,40 @@
+#!/usr/bin/env python3
+# SPDX-License-Identifier: GPL-2.0
+# Configuration file for the Sphinx documentation builder.
+#
+# This file only contains a selection of the most common options. For a full
+# list see the documentation:
+# https://www.sphinx-doc.org/en/master/usage/configuration.html
+
+import os
+import subprocess
+
+project = "libbpf"
+
+extensions = [
+    'sphinx.ext.autodoc',
+    'sphinx.ext.doctest',
+    'sphinx.ext.mathjax',
+    'sphinx.ext.viewcode',
+    'sphinx.ext.imgmath',
+    'sphinx.ext.todo',
+    'breathe',
+]
+
+# List of patterns, relative to source directory, that match files and
+# directories to ignore when looking for source files.
+# This pattern also affects html_static_path and html_extra_path.
+exclude_patterns = []
+
+read_the_docs_build = os.environ.get('READTHEDOCS', None) == 'True'
+
+if read_the_docs_build:
+    subprocess.call('cd sphinx ; make clean', shell=True)
+    subprocess.call('cd sphinx/doxygen ; doxygen', shell=True)
+
+html_theme = 'sphinx_rtd_theme'
+
+breathe_projects = { "libbpf": "./sphinx/doxygen/build/xml/" }
+breathe_default_project = "libbpf"
+breathe_show_define_initializer = True
+breathe_show_enumvalue_initializer = True