vexpress: Set toolchain in Boardconfig.mk

We need not export the TARGET_TOOLS_PREFIX before building.
The patch is dependent on http://review.android.git.linaro.org/#/c/4430/

Change-Id: I09e2c9ead4811be0a1b1d6d4a958e03443700429
Signed-off-by: Vishal Bhoj <vishal.bhoj@linaro.org>
1 file changed