Remove trailing slashes from directories in find command

BSD find is not very smart and ends up writing double slashes into the
output in those cases.  Also, xgettext is not very smart and splits the
file names incorrectly in those cases, resulting in slightly incorrect
file names being written into the POT file.

src/backend/nls.mk

@@ -13,7 +13,7 @@ GETTEXT_FLAGS    = $(BACKEND_COMMON_GETTEXT_FLAGS) \
     report_invalid_record:2:c-format
 
 gettext-files: distprep
-	find $(srcdir)/ $(srcdir)/../common/ $(srcdir)/../port/ -name '*.c' -print | LC_ALL=C sort >$@
+	find $(srcdir) $(srcdir)/../common $(srcdir)/../port -name '*.c' -print | LC_ALL=C sort >$@
 
 my-clean:
 	rm -f gettext-files