Allow fast builds on ppc64le

[mopsfelder]

What type of PR is this?

/kind bug

What this PR does / why we need it:

On a ppc64le host, fast build was failing:

# make KUBE_FASTBUILD=true quick-release
+++ [0908 15:56:36] Verifying Prerequisites....
+++ [0908 15:56:36] Building Docker image kube-build:build-fd009aaa81-5-v1.23.0-go1.17-buster.0
+++ [0908 15:56:44] Syncing sources to container
+++ [0908 15:56:48] Running build command...
+++ [0908 15:56:56] Building go targets for linux/ppc64le:
    ./vendor/k8s.io/code-generator/cmd/prerelease-lifecycle-gen
> non-static build: k8s.io/kubernetes/./vendor/k8s.io/code-generator/cmd/prerelease-lifecycle-gen
touch: cannot touch '_output/bin/prerelease-lifecycle-gen': No such file or directory
make[2]: *** [Makefile.generated_files:209: _output/bin/prerelease-lifecycle-gen] Error 1
make[1]: *** [Makefile:552: generated_files] Error 2
make: *** [Makefile:512: cross] Error 1
!!! [0908 15:56:58] Call tree:
!!! [0908 15:56:58]  1: build/../build/common.sh:476 kube::build::run_build_command_ex(...)
!!! [0908 15:56:58]  2: build/release.sh:36 kube::build::run_build_command(...)
make: *** [Makefile:454: quick-release] Error 1

This error happened because the _output/bin/ directory didn't exist at
the moment the file _output/bin/prerelease-lifecycle-gen was touched, so
the path didn't exist.

The _output/bin symlink was not created by kube::golang::place_bins()
because kube::golang::setup_platforms() assumed
KUBE_CLIENT_PLATFORMS=linux/amd64 despite being on a ppc64le host.

Fix build error by not assuming host_arch=amd64 when on ppc64le in
kube::golang::setup_platforms().

Which issue(s) this PR fixes:

Fixes #105398

Special notes for your reviewer:

This is a minor fix to allow building fast builds on a ppc64le host. Change does not affect other architectures.

Does this PR introduce a user-facing change?

NONE

Additional documentation e.g., KEPs (Kubernetes Enhancement Proposals), usage docs, etc.:

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[neolit123]

looks like arm64 for fast build was added explicitly here:
f719624

unclear if it is desired to add more platforms.

/sig release

[neolit123]

looks like this is a missing feature and not a bug.
/kind feature
/remove-kind bug

[BenTheElder]

/assign @dims
https://github.com/kubernetes/kubernetes/pull/97743/files#r586767541

[dims]

@BenTheElder @neolit123 - with https://github.com/kubernetes/release/pull/1853/files - ppc64le should work fine (kube-cross), so i think this ok.

/ok-to-test

[dims]

/release-note-none

[dims]

/approve
/assign @saschagrunert @mkumatag
(for lgtm)

[mkumatag]

/lgtm
/hold for others to review

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: dims, mkumatag, mopsfelder

The full list of commands accepted by this bot can be found here.

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• hack/OWNERS [dims]

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[BenTheElder]

https://github.com/kubernetes/kubernetes/pull/97743/files#r586161189 stands

[dims]

https://github.com/kubernetes/kubernetes/pull/97743/files#r586161189 stands

yep, for the other platforms, the yard stick would be to ensure kube-cross works first

[dims]

/retest

[BenTheElder]

yep, for the other platforms, the yard stick would be to ensure kube-cross works first

I don't see why we should actively prohibit building on them without a patch though, as opposed to which we choose to ship in our official releases.

[dims]

@BenTheElder oh if it works, sure. the use case here was ... doing a build on arm64 or ppc64le (and that would fail on other platforms). if someone can confirm that it works, then sure!

[mkumatag]

The build did go through on ppc64le platform and here is the log. -Thanks

[BenTheElder]

/priority important-longterm
/triage accepted

[BenTheElder]

/hold cancel