Add n2 and dashmap to the manifest

dashmap is currently unused, but will be required after merging in
https://github.com/evmar/n2/pull/112

Bug: 318434287
Bug: 328273370
Test: added n2 to build-prebuilts.sh, and ran OUT_DIR=out prebuilts/build-tools/build-prebuilts.sh
Change-Id: Ied5af144b8b2c21b385521be430f9d0313c00d93
1 file changed
tree: 21c7540a3139a5410f549bfb185fa7d0905d74f7
  1. default.xml