Fix merge_libs.py to correctly use the IGNORE_PATTERNS list.

The current version accidentally confused two different uses of "in"; it
replaced "substring in string" logic with "item in list" logic, which
won't work for substring matches.

BUG=
R=kjellander@webrtc.org, pthatcher@webrtc.org, tkchin@webrtc.org, tommi@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/47889004

Cr-Commit-Position: refs/heads/master@{#8942}
diff --git a/webrtc/build/merge_libs.py b/webrtc/build/merge_libs.py
index 84904d6..f020594 100644
--- a/webrtc/build/merge_libs.py
+++ b/webrtc/build/merge_libs.py
@@ -36,7 +36,7 @@
   files = []
   for root, _, filenames in os.walk(path):
     for filename in fnmatch.filter(filenames, pattern):
-      if filename not in IGNORE_PATTERNS:
+      if all(pattern not in filename for pattern in IGNORE_PATTERNS):
         # We use the relative path here to avoid "argument list too
         # long" errors on Linux.  Note: This doesn't always work, so
         # we use the find command on Linux.