Build: Set CMAKE_OBJCOPY to default value

On ARMCLANG, set to a default value which matches the cross-compile
triple. This can be overridden on the command-line if needed. Update
usage so that ${CMAKE_OBJCOPY} is used instead of
${CROSS_COMPILE}-objcopy.

Change-Id: I2ca1fe2bf8daa567e0ccab508aa153c2586ddca3
Signed-off-by: Raef Coles <raef.coles@arm.com>
1 file changed