Update README after changes to toolchain development process

Bug: http://b/403137505
Change-Id: I0b9393bee0a747bb89f0517fea9b28ad79aa4ead
1 file changed
tree: b0fbddbd94c1da7c4236acff2304551b7b778998
  1. prebuilts/
  2. toolchain/
  3. .gitattributes
  4. .gitmodules
  5. .supermanifest