avoid shell pwd

Author: kevinushey

src/Makevars.in

@@ -101,7 +101,7 @@ ifeq ($(USE_TBB), Windows)
 
 	# Linker needs access to the tbb dll; otherwise you get errors such as:
 	# "undefined reference to `tbb::task_scheduler_init::terminate()'"
-	PKG_LIBS += -L$(shell pwd)/tbb/build/lib_release -ltbb -ltbbmalloc
+	PKG_LIBS += -Ltbb/build/lib_release -ltbb -ltbbmalloc
 
 endif