DS-5旗舰版编译错误：ARMv8a is a valid option...或者ARM Compiler does not support

使用DS-5编译64位架构内核的时候，提示下面的错误：

armclang: error: ARMv8a is a valid option but it is not supported by this variant of ARM Compiler (ARM Compiler 6.3 Professional)
Please refer to the documentation to make sure you have selected the right tool variant for your license
armclang: error: ARM Compiler does not support '--target=aarch64-arm-none-eabi'

或者

ARMv8a is a valid option but it is not supported by this variant of ARM Compiler (DS-5 Professional 5.23.0 [5230020])

可能是下面的原因引起：

• 没有正确安装或指定License；
• 没有指定 armclang 的目录位置，armclang 在 <DS-5安装目录>/sw/ARMCompiler6.xxx/bin 目录下；
• 使用不支持的编译选项，ARM Compiler 6编译选项新旧对照表请看：http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.dui0742d/chr1372839703185.html