Following D48903 ([VirtualFileSystem] InMemoryFileSystem::status: Return
a Status with the requested name), the paths output by clang-move in the
FileToReplacements map may contain leading "./". For example, where we
would get "foo.h", we'll now get "./foo.h". This breaks the tests,
because we are doing exact string lookups in the FileToFileID and
Results maps (they contain "foo.h", but we search for "./foo.h").
To mitigate this, try to normalize a little bit the paths output by
clang-move to remove that leading "./".
This patch should be safe to merge before D48903, remove_dots will just
be a no-op.