build: Make QEMU_BIN_PATH optional

QEMU_BIN_PATH is frequently set to pick up qemu binaries from "obvious"
places such as /usr/bin or /usr/local/bin. Neither of these values will
be correct for all users and both directories would typically be found
in the user's PATH. Much better to make QEMU_BIN_PATH optional and picking
up qemu via PATH instead.

Tested with ZEPHYR_GCC_VARIANT={zephyr|xtools}.

Change-Id: I1acfc5b12341c6d330a3e9e90b0ab5bde29e2e4f
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
Cc: Andrew Boie <andrew.p.boie@intel.com>
2 files changed