add more testcases for prebuilt objects

Cover more cases including passing objects via ExtractedObjects and
CustomTarget.

test cases/unit/15 prebuilt object/cp.py

@@ -0,0 +1,5 @@
+#! /usr/bin/env python3
+
+import sys
+from shutil import copyfile
+copyfile(*sys.argv[1:])

test cases/unit/15 prebuilt object/meson.build

@@ -19,7 +19,22 @@ endif
 # declaration. run_tests.py generates the
 # prebuilt object before running this test.
 
-e = executable('prog', 'main.c',
-objects : prebuilt)
+e = []
 
-test('objtest', e)
+e += executable('exe1', sources: 'main.c', objects: prebuilt)
+e += executable('exe2', sources: 'main.c', objects: files(prebuilt))
+
+sl1 = static_library('lib3', objects: prebuilt)
+e += executable('exe3', sources: 'main.c', objects: sl1.extract_all_objects(recursive: true))
+
+ct = custom_target(output: 'copy-' + prebuilt, input: prebuilt,
+                   command: [find_program('cp.py'), '@INPUT@', '@OUTPUT@'])
+e += executable('exe4', 'main.c', ct)
+e += executable('exe5', 'main.c', ct[0])
+
+sl2 = static_library('lib6', sources: ct)
+e += executable('exe6', sources: 'main.c', objects: sl2.extract_all_objects(recursive: true))
+
+foreach i : e
+  test(i.name(), i)
+endforeach