io/uring: basic Linux io_uring support

src/io/uring/meson.build

@@ -0,0 +1,36 @@
+uring_features = configuration_data()
+
+if host_machine.system() != 'linux'
+  uring_dep = dependency('', required: false)
+  uring_features.set('HAVE_URING', false)
+  configure_file(output: 'Features.h', configuration: uring_features)
+  subdir_done()
+endif
+
+liburing = dependency('liburing', required: get_option('io_uring'))
+uring_features.set('HAVE_URING', liburing.found())
+configure_file(output: 'Features.h', configuration: uring_features)
+
+if not liburing.found()
+  uring_dep = dependency('', required: false)
+  subdir_done()
+endif
+
+uring = static_library(
+  'uring',
+  'Ring.cxx',
+  'Queue.cxx',
+  'Operation.cxx',
+  include_directories: inc,
+  dependencies: [
+    liburing,
+  ],
+)
+
+uring_dep = declare_dependency(
+  link_with: uring,
+  dependencies: [
+    liburing,
+    io_dep,
+  ],
+)