[libfuzzer] Error out if any of seed_corpus directories does not exist.

This CL might break libFuzzer builders if there are invalid paths specified in
corresponding GN targets. We will have to fix those path in that case.

[email protected]

Bug: 751810
Change-Id: I143deb5cc5e3ccf67e9a61b0ad343ae3a64905ad
Reviewed-on: https://chromium-review.googlesource.com/598643
Commit-Queue: Max Moroz <[email protected]>
Reviewed-by: Pavel Feldman <[email protected]>
Reviewed-by: Lei Zhang <[email protected]>
Reviewed-by: Dirk Pranke <[email protected]>
Reviewed-by: Oliver Chang <[email protected]>
Cr-Commit-Position: refs/heads/master@{#492559}
diff --git a/testing/libfuzzer/archive_corpus.py b/testing/libfuzzer/archive_corpus.py
index 9d3bf93..a3fd29f 100755
--- a/testing/libfuzzer/archive_corpus.py
+++ b/testing/libfuzzer/archive_corpus.py
@@ -28,6 +28,9 @@
   corpus_files = []
 
   for directory in args.corpus_directories:
+    if not os.path.exists(directory):
+      raise Exception('The given seed_corpus directory (%s) does not exist.' %
+                      directory)
     for (dirpath, _, filenames) in os.walk(directory):
       for filename in filenames:
         full_filename = os.path.join(dirpath, filename)