TestDispatchFromFlagsAndUseBuiltInArgs fails on arm

[siretart]

#224 introduces a test that fail on arm64, armhf and armel with:

On arm64:

=== RUN   TestDispatchFromFlagsAndUseBuiltInArgs
    dispatchers_test.go:798: Expected linux/arm64, to match linux/arm64/v8
--- FAIL: TestDispatchFromFlagsAndUseBuiltInArgs (0.00s)

on armel:

=== RUN   TestDispatchFromFlagsAndUseBuiltInArgs
    dispatchers_test.go:798: Expected linux/arm, to match linux/arm/v8
--- FAIL: TestDispatchFromFlagsAndUseBuiltInArgs (0.00s)

On armhf:

=== RUN   TestDispatchFromFlagsAndUseBuiltInArgs
    dispatchers_test.go:798: Expected linux/arm, to match linux/arm/v7
--- FAIL: TestDispatchFromFlagsAndUseBuiltInArgs (0.00s)

[openshift-bot]

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/lifecycle stale

[siretart]

/remove-lifecycle stale

[rhatdan]

@flouthoc @nalind PTAL

[nalind]

I don't have easy access to most of the affected platforms, but #272 at least does the right thing in my aarch64 VM.