Fix coupling with sassc makefile

SassC was previously linking to the local shared library
which was not what we wanted when the library was used in
a system install (since removing the build directory would
result in the linked library not being found anymore).

Author: mgreter

Makefile

@@ -299,7 +299,7 @@ install-shared: $(DESTDIR)$(PREFIX)/lib/libsass.so \
                 install-headers
 
 $(SASSC_BIN): $(BUILD)
-	$(MAKE) -C $(SASS_SASSC_PATH)
+	$(MAKE) -C $(SASS_SASSC_PATH) build-$(BUILD)-dev
 
 sassc: $(SASSC_BIN)
 	$(SASSC_BIN) -v