Added test cases for tuning (coming from torch frontend)

hpvm/test/lit.site.cfg.py.in

@@ -10,4 +10,5 @@ import lit.llvm
 lit.llvm.initialize(lit_config, config)
 
 # Let the main config do the real work.
-lit_config.load_config(config, "@CMAKE_CURRENT_SOURCE_DIR@/lit.cfg.py")
+# (ARG_MAIN_CONFIG is a variable defined in configure_lit_site_cfg)
+lit_config.load_config(config, "@ARG_MAIN_CONFIG@")