Ensure availability of all required libdispatch artifacts

Make sure all libdispatch build artifacts are availlable before adding
the libdispatch lit test feature.

Author: yln

test/lit.cfg

@@ -912,14 +912,19 @@ elif run_os in ['linux-gnu', 'linux-gnueabihf', 'freebsd', 'windows-cygnus', 'wi
     config.target_runtime = "native"
     config.target_swift_autolink_extract = inferSwiftBinary("swift-autolink-extract")
 
-    config.libdispatch_build_dir = make_path(config.swift_obj_root, os.pardir,
+    libdispatch_build_dir = make_path(config.swift_obj_root, os.pardir,
         'libdispatch%s' % config.variant_suffix, 'src')
-    if os.path.exists(config.libdispatch_build_dir):
+    libdispatch_build_artifacts = [
+        make_path(libdispatch_build_dir, 'libdispatch.so'),
+        make_path(libdispatch_build_dir, 'libswiftDispatch.so'),
+        make_path(libdispatch_build_dir, 'swift', 'Dispatch.swiftmodule')]
+    if (all(os.path.exists(p) for p in libdispatch_build_artifacts)):
         config.available_features.add('libdispatch')
+        config.libdispatch_build_dir = libdispatch_build_dir
         source_dir = make_path(config.swift_src_root, os.pardir, 'swift-corelibs-libdispatch')
-        swift_module_dir = make_path(config.libdispatch_build_dir, 'swift')
+        swift_module_dir = make_path(libdispatch_build_dir, 'swift')
         config.import_libdispatch = ('-I %s -I %s -L %s'
-            % (source_dir, swift_module_dir, config.libdispatch_build_dir))
+            % (source_dir, swift_module_dir, libdispatch_build_dir))
 
     config.target_build_swift = (
         '%s -target %s %s %s %s %s %s'