[lit] Add a --filter option which is useful when dealing with virtual test paths.
[lit] Add a --filter option which is useful when dealing with virtual test
paths.

git-svn-id: a4a6f32337ebd29ad4763b423022f00f68d1c7b7@148362 91177308-0d34-0410-b5e6-96231b3b80d8

lodyagin/bare_cxx,lodyagin/bare_cxx,lodyagin/bare_cxx,lodyagin/bare_cxx,lodyagin/bare_cxx