Set landmines on x64 too.

For some reason I was only setting up landmines in the 32 bit output folders.
This will allow us to clobber on x64 builds too.

R=ilevy@chromium.org
BUG=

Review URL: https://codereview.chromium.org/13133005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@191446 0039d316-1c4b-4281-b951-d872f2087c98

Author: iannucci@chromium.org

build/landmines.py

@@ -223,7 +223,7 @@ def main():
 
   gyp_helper.apply_chromium_gyp_env()
 
-  for target in ('Debug', 'Release'):
+  for target in ('Debug', 'Release', 'Debug_x64', 'Release_x64'):
     set_up_landmines(target)
 
   return 0