Teach the test runner whether it's running on a trybot or not

tools/run-tests.py

Index: tools/run-tests.py
diff --git a/tools/run-tests.py b/tools/run-tests.py
index d793a8ae71532f33c88640b6892621e5ca6b9321..d68d1f86bdd80cfff1bff70e2928ead790c4e136 100755
--- a/tools/run-tests.py
+++ b/tools/run-tests.py
@@ -141,6 +141,9 @@ def BuildOptions():
   result.add_option("--buildbot",
                     help="Adapt to path structure used on buildbots",
                     default=False, action="store_true")
+  result.add_option("--dcheck-always-on",
+                    help="Indicates that V8 was compiled with DCHECKs enabled",
+                    default=False, action="store_true")
   result.add_option("--cat", help="Print the source of the tests",
                     default=False, action="store_true")
   result.add_option("--flaky-tests",
@@ -508,6 +511,7 @@ def Execute(arch, mode, args, options, suites, workspace):
     "system": utils.GuessOS(),
     "tsan": options.tsan,
     "msan": options.msan,
+    "dcheck_always_on": options.dcheck_always_on,
   }
   all_tests = []
   num_tests = 0