Don't stage removals in git when --skip-cls is used.

--skip-cls is supposed to leave out git, including the staging index.

Test: art/build/update-art-module-prebuilts.py \
      --skip-cls --local-dist=...
Bug: 172480615
Change-Id: I58ad4ac573241b1c83400258932f1de8a0ba0cea
1 file changed