Xcode: skip all-object library test.
project('extract all', 'c', 'cpp')
+if meson.backend() == 'xcode'
+ error('MESON_SKIP_TEST: Xcode backend does not handle libraries with only objects, not sources.')
+endif
+
a = static_library('a', 'one.c', 'two.c')
b = static_library('b', 'three.c', 'four.c')
c = shared_library('c',
