Ignore unsupport host architectures for binutils download.

BUG=v8:3880
LOG=n
TBR=svenpanne@chromium.org

Review URL: https://codereview.chromium.org/908173002

Cr-Commit-Position: refs/heads/master@{#26537}

third_party/binutils/download.py

@@ -110,8 +110,7 @@ def main(args):
       return ret
     # Fetch the x64 toolchain as well for official bots with 64-bit kernels.
     return FetchAndExtract('x64')
-  print "Host architecture %s is not supported." % arch
-  return 1
+  return 0
 
 
 if __name__ == '__main__':