Match libfuzzer's timeout for reproduction in centipede (#5291)

Libfuzzer uses `TEST_TIMEOUT - 5`, ignoring fuzzer-defined timeouts, as
the per input timeout when reproducing a crash. This PR changes
Centipede to also override fuzzer-defined timeouts and use `TEST_TIMEOUT
- 5`.

Author: g-ortuno

src/clusterfuzz/_internal/bot/fuzzers/centipede/engine.py

@@ -433,11 +433,12 @@ def reproduce(self, target_path, input_path, arguments, max_time):  # pylint: di
       rss_limit = constants.RSS_LIMIT_MB_DEFAULT
       if constants.RSS_LIMIT_MB_FLAGNAME in fuzzer_arguments:
         rss_limit = fuzzer_arguments[constants.RSS_LIMIT_MB_FLAGNAME]
-
-      timeout = constants.TIMEOUT_PER_INPUT_REPR_DEFAULT
-      if constants.TIMEOUT_PER_INPUT_FLAGNAME in fuzzer_arguments:
-        timeout = fuzzer_arguments[constants.TIMEOUT_PER_INPUT_FLAGNAME]
-
+      # Override fuzzer-defined timeouts to match libfuzzer's behavior in
+      # https://github.com/google/clusterfuzz/blob/d15a65e7753c6c6579f4b395c40e6d45a7bde262/src/clusterfuzz/_internal/bot/fuzzers/libfuzzer.py#L1255
+      test_timeout = environment.get_value(
+          'TEST_TIMEOUT', constants.TIMEOUT_PER_INPUT_REPR_DEFAULT)
+      # Leave 5 sec buffer for report processing.
+      timeout = max(1, test_timeout - 5)
       os.environ['CENTIPEDE_RUNNER_FLAGS'] = (
           f':{constants.RSS_LIMIT_MB_FLAGNAME}={rss_limit}'
           f':{constants.TIMEOUT_PER_INPUT_FLAGNAME}={timeout}:')