build: fix icutrim when building small-icu on BE

Fix a build error that occurs when icutrim is run to cut down
the ICU locale set on Big-Endian platforms when building with
--with-intl=small-icu (which is done by the "make binary" target).
This fixes the binary build on POWER platforms.

Fixes: https://github.com/nodejs/node/issues/2601
PR-URL: https://github.com/nodejs/node/pull/2602


Reviewed-By: Steven Loomis <srloomis@us.ibm.com>