[LIT] Don't exit after showing all discovered tests

[madhur13490]

Summary

It is useful to continue than exit as it shows the summary
at the top.

llvm/utils/lit/lit/cl_arguments.py

debug_group.add_argument(
         "--debug", help="Enable debugging (for 'lit' development)", action="store_true"
     )
     debug_group.add_argument(
         "--show-suites",
         help="Show discovered test suites and exit",
         action="store_true",
     )
     debug_group.add_argument(
-        "--show-tests", help="Show all discovered tests and exit", action="store_true"
+        "--show-tests", help="Show all discovered tests", action="store_true"
     )
     debug_group.add_argument(
         "--show-used-features",
         help="Show all features used in the test suite (in XFAIL, UNSUPPORTED and REQUIRES) and exit",
         action="store_true",
     )
 
     # LIT is special: environment variables override command line arguments.

llvm/utils/lit/lit/main.py

discovered_tests = lit.discovery.find_tests_for_inputs(
         lit_config, opts.test_paths
     )
     if not discovered_tests:
         sys.stderr.write("error: did not discover any tests for provided path(s)\n")
         sys.exit(2)
 
     if opts.show_suites or opts.show_tests:
         print_discovered(discovered_tests, opts.show_suites, opts.show_tests)
-        sys.exit(0)
 
     if opts.show_used_features:
         features = set(
             itertools.chain.from_iterable(
                 t.getUsedFeatures()
                 for t in discovered_tests
                 if t.gtest_json_file is None
             )