Build: Add back TFM_CODE_COVERAGE setting in GNUARM toolchain

TFM_CODE_COVERAGE was removed by accident from toolchain_GNUARM.cmake.
Add it back.

Change-Id: I2cdd5f57963d36b094c05ffcc930de371e725600
Signed-off-by: David Hu <david.hu@arm.com>
1 file changed