fix for the tests the DPS_TOOLKIT_HOME setting in Makefiles

Author: ZollnaPa

samples/DPSUsageFromCpp/Makefile

@@ -31,7 +31,7 @@
 # present in the DPS toolkit's impl directory, it is necessary to
 # export the following. This will get used inside the C++ operator's
 # impl/bin/archLevel file.
-export DPS_TOOLKIT_HOME=$(HOME)/streamsx.dps/com.ibm.streamsx.dps
+export DPS_TOOLKIT_HOME?=$(HOME)/streamsx.dps/com.ibm.streamsx.dps
 
 SPLC_FLAGS ?= -a -t $(DPS_TOOLKIT_HOME)
 SPLC = $(STREAMS_INSTALL)/bin/sc

samples/advanced/04_all_dps_apis_at_work_in_spl/Makefile

@@ -25,7 +25,7 @@
 # Since the DPS toolkit version you are using could be more
 # recent than the one in the IBM Streams installation directory,
 # you may want to ensure that the following DPS toolkit path is correct.
-DPS_TOOLKIT_HOME = $(HOME)/streamsx.dps/com.ibm.streamsx.dps
+DPS_TOOLKIT_HOME ?= $(HOME)/streamsx.dps/com.ibm.streamsx.dps
 
 # If the user wants to use a different version of
 # the DPS toolkit than the one shipped in the