Update README after changes to toolchain development process

Bug: http://b/403137505
Change-Id: I0b9393bee0a747bb89f0517fea9b28ad79aa4ead
1 file changed
tree: be60a2a3c95ce9ba50a6b9472dc582e4d86fd3d9
  1. external/
  2. prebuilts/
  3. .gitattributes
  4. .gitmodules
  5. .supermanifest