[meson] introduce new option which is passed to emper

meson.build

@@ -16,17 +16,9 @@ conf_data = configuration_data()
 option_async_io = get_option('async_io')
 conf_data.set('USE_ASYNC_IO', option_async_io)
 
-option_try_syscall = get_option('try_syscall')
-if option_try_syscall
-	if not option_async_io
-		error('try_syscall defined without async_io')
-	endif
-
-	emper_proj = subproject('emper', default_options: ['async_lib=true', 'async_lib_try_syscall=true'])
-else
-	emper_proj = subproject('emper', default_options: ['async_lib=true'])
-endif
+emper_options = get_option('emper_options')
 
+emper_proj = subproject('emper', default_options: emper_options)
 emper_dep = emper_proj.get_variable('emper_dep')
 dependencies = [emper_dep]
 

meson_options.txt

+option('emper_options', type: 'array', value: [])
 option('async_io', type: 'boolean', value: true)
-option('try_syscall', type: 'boolean', value: true)