Blind "fix" for when using system ICU

No point in pointing to nonexistent ICU headers in solver if building
against a system ICU.

Change-Id: I5a151f3bfefd1913ad84a33d74af749558926312

libcdr/ExternalProject_libcdr.mk

@@ -61,8 +61,7 @@ else
 $(call gb_ExternalProject_get_state_target,libcdr,build) :
 	cd $(EXTERNAL_WORKDIR) \
 	&& export PKG_CONFIG="" \
-	&& export ICU_LIBS=" " \
-	&& export ICU_CFLAGS="-I$(OUTDIR)/inc/external" \
+	&& $(if $(filter NO,$(SYSTEM_ICU)), export ICU_LIBS=" " ICU_CFLAGS="-I$(OUTDIR)/inc/external") \
 	&& ./configure \
 		--with-pic \
 		--enable-static \