Bug description

Using MacOS, BUILD_WITH_CONTAINER=1 make istioctl.completion fails

/work/out/darwin_amd64/istioctl collateral --bash && \
mv istioctl.bash /work/out/darwin_amd64/release/istioctl.bash
/bin/bash: /work/out/darwin_amd64/istioctl: cannot execute binary file: Exec format error
Makefile.core.mk:361: recipe for target '/work/out/darwin_amd64/release/istioctl.bash' failed

The issue is that the makefile running on Linux in the container is trying to run a MacOS binary crated during the build process.

Expected behavior

BUILD_WITH_CONTAINER=1 make istioctl.completion shown run successfully on a Mac

Steps to reproduce the bug

Prepare MacOS development as specified.

Run BUILD_WITH_CONTAINER=1 make istioctl.completion

Version (include the output of istioctl version --remote and kubectl version and helm version if you used Helm)

Current master branch

How was Istio installed?

N/A

Environment where bug was observed (cloud vendor, OS, etc)

macOS Catalina