[MacOS] Make qemu and frdm_k64f target failed

[qiaojingx]

Description

This is a regression issue. Error running link command occurs when building qemu and frdm_k64f target on Mac.

Test Code

HelloWorld.js;

Steps to Reproduction

1. Building qemu target on MAC by follow instructions: building-qemu-and-arduino-101-targets
   make JS=samples/HelloWorld.js BOARD=qemu_x86 qemu

2. Building frdm_k64f target on MAC:
   make JS=samples/HelloWorld.js BOARD=frdm_k64f CROSS_COMPILE=~/Downloads/gcc-arm-none-eabi-6-2017-q1-update/bin/arm-none-eabi-

Actual Result

1. Building qemu target failed on Mac:(you may met error No such file or directory: CMAKE_READELF first, then need to modify i586-zephyr-elfiamcu to i586-zephyr-elf in ${ZEPHYR_BASE}/cmake/toolchain/xtools.cmake)

2. Building frdm_k64f target failed on Mac:

Expected Result

Building successfully.

Test Builds

Branch	Commit Id	Target Device	Test Date	Result
master	f90d9d1	qemu	May 23, 2017	Fail
master	f90d9d1	frdm_k64f	May 23, 2018	Fail

Additional Information