message: Use := instead of ?= to set MAKEFILES_DIR to fix Android build flakiness
diff: # Host compilation settings
  # Find where we're running from, so we can store generated files here.
  -MAKEFILE_DIR ?= $(shell dirname $(realpath $(lastword $(MAKEFILE_LIST))))
  +ifeq ($(origin MAKEFILE_DIR), undefined)
  + MAKEFILE_DIR := $(shell dirname $(realpath $(lastword $(MAKEFILE_LIST))))
  +endif
  HAS_GEN_HOST_PROTOC := \
  $(shell test -f $(MAKEFILE_DIR)/gen/protobuf-host/bin/protoc && echo "true" ||\
  echo "false")
  