add istioctl build for ARMv7 and ARM64 (#22381)
add istioctl build for ARMv7 and ARM64 (#22381)

* add istioctl build for ARMv7 and ARM64

* corrected typo to restore amd64

* Update Makefile.core.mk

revert build filename to isitioctl-linux for amd64

* duplicated istioctl-linux as istioctl-linux-amd64

* minor formatting

* minor formatting
smawson/istio,istio/istio,smawson/istio,istio/istio,smawson/istio,istio/istio,smawson/istio,smawson/istio,istio/istio,istio/istio,smawson/istio