test: fix test-module-loading-error for musl

When a compiled library file does not have the proper format,
musl returns the error message ENOEXEC as 'Exec format error' but
glibc returns 'file too short' if the file is under a certain size.

Reference:
http://git.musl-libc.org/cgit/musl/tree/src/errno/__strerror.h#n46

This patch consists of tolerating musl's error.

PR-URL: https://github.com/nodejs/node/pull/3657


Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Johan Bergström <bugs@bergstroem.nu>