Update build image version to pr9070-2850516d73

Author: alexweav

Makefile

@@ -275,7 +275,7 @@ mimir-build-image/$(UPTODATE): mimir-build-image/*
 # All the boiler plate for building golang follows:
 SUDO := $(shell docker info >/dev/null 2>&1 || echo "sudo -E")
 BUILD_IN_CONTAINER ?= true
-LATEST_BUILD_IMAGE_TAG ?= pr8600-8a8fd767c7
+LATEST_BUILD_IMAGE_TAG ?= pr9070-2850516d73
 
 # TTY is parameterized to allow Google Cloud Builder to run builds,
 # as it currently disallows TTY devices. This value needs to be overridden