Updates to the relocation api

Summary: More changes needed for live code relocation

Reviewed By: @bertmaher

Differential Revision: D1699527

Signature: t1:1699527:1416864528:bf9653d5abed5fdeaf7f7d7a1fa4e193a5ff2bdd
Add extra stats recording to hack build

Summary: Record more information on CLIENT_BUILD_FINISH events

Reviewed By: @​jcreed

Differential Revision: D1702101

Signature: t1:1702101:1416933067:d916946c13238a2dc2114fa2fb85fa697018827a