meson: add option for librist support

meson_options.txt

@@ -596,6 +596,11 @@ option('udev',
     value: 'auto',
     description: 'Linux udev services discovery')
 
+option('rist',
+    type: 'feature',
+    value: 'auto',
+    description: 'librist support for access and access_output')
+
 # TODO: Missing live555
 # TODO: Missing v4l2
 # TODO: Missing nvdec

modules/meson.build

@@ -127,7 +127,7 @@ endif
 srt_dep = dependency('srt', version: '>=1.3.0', required: get_option('srt'))
 
 # libRist
-librist_dep = dependency('librist', required: false)
+librist_dep = dependency('librist', required: get_option('rist'))
 
 # MTP
 mtp_dep = dependency('libmtp', version: '>=1.0.0', required: get_option('mtp'))