runtime: in asan mode unregister root regions on free
CL 651755 introduced registration of root regions when allocating
memory. We also need to unregister that memory to avoid the leak
sanitizer accessing unmapped memory.
Issue #67833
Change-Id: I5d403d66e65a8a003492f4d79dad22d416fd8574
Reviewed-on: https://go-review.googlesource.com/c/go/+/659135
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com> Reviewed-by: Ian Lance Taylor <iant@google.com>