Documentation: Move all dependencies into features

This way if the user enables the documentation and the dependencies are
missing the configure fails.

Suggested-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Ricardo Ribalda <ricardo@ribalda.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

Documentation/meson.build

@@ -7,8 +7,8 @@ doc_install_dir = join_paths(get_option('datadir'), 'doc',
 # Doxygen
 #
 
-doxygen = find_program('doxygen', required : false)
-dot = find_program('dot', required : false)
+doxygen = find_program('doxygen', required : get_option('documentation'))
+dot = find_program('dot', required : get_option('documentation'))
 
 if doxygen.found() and dot.found()
     cdata = configuration_data()
@@ -42,7 +42,7 @@ endif
 
 sphinx = find_program('sphinx-build-3', required : false)
 if not sphinx.found()
-    sphinx = find_program('sphinx-build', required : false)
+    sphinx = find_program('sphinx-build', required : get_option('documentation'))
 endif
 
 if sphinx.found()

meson.build

@@ -110,9 +110,7 @@ subdir('src')
 # The documentation and test components are optional and can be disabled
 # through configuration values. They are enabled by default.
 
-if get_option('documentation')
 subdir('Documentation')
-endif
 
 if get_option('test')
     subdir('test')

meson_options.txt

@@ -6,7 +6,7 @@ option('android',
         description : 'Compile libcamera with Android Camera3 HAL interface')
 
 option('documentation',
-        type : 'boolean',
+        type : 'feature',
         description : 'Generate the project documentation')
 
 option('gstreamer',