meson: add htmldocs option for installing the docs

Currently there is a limited set of documentation installed by default.
We already have the sphinx docs wired into the meson build, although
there is no way for the end-user to install them.

Add an `htmldocs` option which guards both build and install of the
docs. Thus people can opt out of, even if they have sphinx installed.

Issue: rauc#1251
Signed-off-by: Emil Velikov <emil.l.velikov@gmail.com>

docs/meson.build

@@ -1,9 +1,9 @@
-sphinx = find_program('sphinx-build', required: false)
-
-if not sphinx.found()
+if not get_option('htmldocs')
   subdir_done()
 endif
 
+sphinx = find_program('sphinx-build')
+
 sources_doc = files([
   'conf.py',
   'advanced.rst',
@@ -27,5 +27,6 @@ custom_target(
   output: 'html',
   depend_files: sources_doc,
   command: [sphinx, '-b', 'html', meson.current_source_dir(), meson.current_build_dir() / 'html'],
-  build_by_default: false
+  install: true,
+  install_dir: join_paths(datadir, 'doc', 'rauc'),
 )

meson_options.txt

@@ -60,6 +60,11 @@ option(
   description : 'D-Bus interfaces directory')
 
 # build options
+option(
+  'htmldocs',
+  type : 'boolean',
+  value : 'true',
+  description : 'Enable/Disable html documentation')
 option(
   'tests',
   type : 'boolean',