[libFuzzer] Docs: add a note regarding "odr-violation" errors.

Bug: 539572
Change-Id: I721b224671ead0b1f6852269667f525c7abb08ed
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1715107
Commit-Queue: Max Moroz <mmoroz@chromium.org>
Auto-Submit: Max Moroz <mmoroz@chromium.org>
Reviewed-by: Jonathan Metzman <metzman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#680079}

testing/libfuzzer/getting_started.md

@@ -117,6 +117,10 @@ INFO: A corpus is not provided, starting from an empty corpus
 For more information about libFuzzer's output, please refer to [its own
 documentation].
 
+*Note*: if you observe an `odr-violation` error in the log, please try setting
+the following environment variable: `ASAN_OPTIONS=detect_odr_violation=0` and
+running the fuzz target again.
+
 ### Symbolize Stacktrace
 
 If your fuzz target crashes when running locally and you see non-symbolized