makefile: improve out of ORFS tree use-case

Signed-off-by: Øyvind Harboe <[email protected]>

Author: oharboe

flow/Makefile

@@ -123,7 +123,7 @@ SHELL          := /usr/bin/env bash
 #   location
 # - default is current install / clone directory
 ifeq ($(origin FLOW_HOME), undefined)
-FLOW_HOME := $(shell pwd)
+FLOW_HOME := $(abspath $(dir $(firstword $(MAKEFILE_LIST))))
 endif
 export FLOW_HOME