make update-po problem with USE_PGXS

Hi,

I'm developing an extension, after modifying some source file(add some message
like gettext('xxxxx')) and execute

$ make USE_PGXS=1 update-po
make: Nothing to be done for 'update-po'.

I feel strange because I think *.po.new files should be created.

After some research, I find in $pginstall/lib/postgresql/pgxs/src/nls-global.mk

ifneq (,$(filter update-po %.po.new,$(MAKECMDGOALS)))
ALL_LANGUAGES := $(shell find $(top_srcdir) -name '*.po' -print | sed 's,^.*/\([^/]*\).po$$,\1,' | LC_ALL=C sort -u)
all_compendia := $(shell find $(top_srcdir) -name '*.po' -print | LC_ALL=C sort)
else

When USE_PGXS is on, the value of $(top_srcdir) is

$pginstall/lib/postgresql/pgxs/src/makefiles/../..

Therefore, command find will nerver find any po file.

I think this is a problem and plan to modify this,
when USE_PGXS is on, we can use:
find . -name '*.po' -print

Or there are some advice/comments?

Regards
Shenhao Wang