all: $(SUB_DIRS)
 
 $(SUB_DIRS):
-       BUILD_TARGET=$$OUTPUT/$@; mkdir -p $$BUILD_TARGET; $(MAKE) OUTPUT=$$BUILD_TARGET -k -C $@ all
+       BUILD_TARGET=$(OUTPUT)/$@; mkdir -p $$BUILD_TARGET; $(MAKE) OUTPUT=$$BUILD_TARGET -k -C $@ all
 
 include ../lib.mk
 
 override define RUN_TESTS
        @for TARGET in $(SUB_DIRS); do \
-               BUILD_TARGET=$$OUTPUT/$$TARGET; \
+               BUILD_TARGET=$(OUTPUT)/$$TARGET;        \
                $(MAKE) OUTPUT=$$BUILD_TARGET -C $$TARGET run_tests;\
        done;
 endef
 
 override define INSTALL_RULE
        @for TARGET in $(SUB_DIRS); do \
-               BUILD_TARGET=$$OUTPUT/$$TARGET; \
+               BUILD_TARGET=$(OUTPUT)/$$TARGET;        \
                $(MAKE) OUTPUT=$$BUILD_TARGET -C $$TARGET install;\
        done;
 endef
 
 override define EMIT_TESTS
        @for TARGET in $(SUB_DIRS); do \
-               BUILD_TARGET=$$OUTPUT/$$TARGET; \
+               BUILD_TARGET=$(OUTPUT)/$$TARGET;        \
                $(MAKE) OUTPUT=$$BUILD_TARGET -s -C $$TARGET emit_tests;\
        done;
 endef
 
 clean:
        @for TARGET in $(SUB_DIRS); do \
-               BUILD_TARGET=$$OUTPUT/$$TARGET; \
+               BUILD_TARGET=$(OUTPUT)/$$TARGET;        \
                $(MAKE) OUTPUT=$$BUILD_TARGET -C $$TARGET clean; \
        done;
        rm -f tags