Reverting manifest revert now that valgrind repos are fixed.

Revert "Reverting valgrind/vex commits (Bug 854517 e16fe0ebb94ef527bea4876b4ef994fb4c577d8a e819e3792dfe2b2f434261b2e47e2279830de45f) due to emulator bustage"

This reverts commit 0931407d1b2689fb8d08ba25683ab558bf47d920.