Update build-tools to ab/4801238

Major updates:
* Merged in the latest ninja release (v1.8.2)
* Added flex

Looks like there are updates in a bunch of other projects too.

Test: m
Change-Id: I33f00e915bf008698a737dc1a4d6f4854b8aa772
47 files changed
tree: e4d1c112ef700e05b1b2e6582a077a9abf67adff
  1. common/
  2. darwin-x86/
  3. linux-x86/
  4. build-prebuilts.sh
  5. manifest.xml
  6. OWNERS