--- a/make-rules/shared-macros.mk	Fri Aug 26 09:16:11 2016 -0700
+++ b/make-rules/shared-macros.mk	Fri Aug 26 16:37:59 2016 -0700
@@ -459,8 +459,8 @@
 # BUILD_TOOLS is the root of all tools not normally installed on the system.
 BUILD_TOOLS ?=	/ws/on12-tools
 
-SPRO_ROOT =	$(BUILD_TOOLS)/SUNWspro
-SPRO_VROOT =	$(SPRO_ROOT)/solarisstudio12.4
+SPRO_ROOT ?=	$(BUILD_TOOLS)/SUNWspro
+SPRO_VROOT ?=	$(SPRO_ROOT)/solarisstudio12.4
 
 PARFAIT_ROOT =	$(BUILD_TOOLS)/parfait/parfait-tools-1.8.0.1
 PARFAIT_TOOLS=	$(WS_TOOLS)/$(MACH)/parfait