cpplint: Allow mutable references

As of May 2020 the Google C++ Style Guide suggests using references
for out paramters. Adjust V8's presubmit checks to allow mutable
reference parameters.

Bug: v8:10624
Change-Id: Idcd027892916a14f91ca3bfcb5eba48757cab523
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2252185Reviewed-by: Hannes Payer <hpayer@chromium.org>
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68449}

tools/v8_presubmit.py

@@ -59,12 +59,16 @@ from testrunner.local import utils
 #   We now run our own header guard check in PRESUBMIT.py.
 # build/include_what_you_use: Started giving false positives for variables
 #   named "string" and "map" assuming that you needed to include STL headers.
+# runtime/references: As of May 2020 the C++ style guide suggests using
+#   references for out parameters, see
+#   https://google.github.io/styleguide/cppguide.html#Inputs_and_Outputs.
 
 LINT_RULES = """
 -build/header_guard
 -build/include_what_you_use
 -readability/fn_size
 -readability/multiline_comment
+-runtime/references
 -whitespace/comments
 """.split()