[llvm-symbolizer] Quick fix for broken sanitizer bot

(sanitizer-x86_64-linux) until I can triage the issue properly. The
build has been broken due to the symbolizer build checks failing.

As the symbolizer build script relies on the old svn repo layout, it may
take a little while longer to find the responsible patch for the
breakage. This may be a completely valid fix, but I will need to confirm
it. For now, it unbreaks the build.

Tracking data:
Build where the break first occurred: http://lab.llvm.org:8011/builders/sanitizer-x86_64-linux/builds/21211
Changelist authors: @grimar, @maskray, @whitequark, @spatel, @dpreobra

For the authors, no action needed (yet). Will follow up when I can
identify the cause.

llvm-svn: 359123