OpenBSD: no -lrt ; add epoll-shim

Index: meson.build
--- meson.build.orig
+++ meson.build
@@ -12,6 +12,8 @@ project(
 
 cc = meson.get_compiler('c')
 
+is_openbsd = host_machine.system().startswith('openbsd')
+
 add_project_arguments(cc.get_supported_arguments([
 	'-DVERSION="@0@"'.format(meson.project_version()),
 
@@ -28,7 +30,8 @@ wayland_client  = dependency('wayland-client')
 wayland_protos  = dependency('wayland-protocols')
 xkbcommon       = dependency('xkbcommon')
 
-rt = cc.find_library('rt')
+epoll = dependency('epoll-shim', required: is_openbsd)
+rt = cc.find_library('rt', required: not is_openbsd)
 
 subdir('protocols')
 subdir('docs')
@@ -49,6 +52,7 @@ executable(
 		pango,
 		pangocairo,
 		rt,
+		epoll,
 		wayland_client,
 		wayland_protos,
 		xkbcommon,
@@ -72,6 +76,7 @@ executable(
 		pango,
 		pangocairo,
 		rt,
+		epoll,
 		wayland_client,
 		wayland_protos,
 		xkbcommon,
