fix: arm64 image is actually x86

[nhamlh]

BUILDPLATFORM is host platform architecture, in this case, Github Action runner, not the architecture of produced image artifact.

From the screenshot bellow we can see that linux/arm64 image sourced photon x86:

[vmwclabot]

@nhamlh, you must sign every commit in this pull request acknowledging our Developer Certificate of Origin before your changes are merged. This can be done by adding Signed-off-by: John Doe <john.doe@email.org> to the last line of each Git commit message. The e-mail address used to sign must match the e-mail address of the Git author. Click here to view the Developer Certificate of Origin agreement.

• Commit c87641b must be signed by lehoainham@gmail.com

[vmwclabot]

@nhamlh, you must sign every commit in this pull request acknowledging our Developer Certificate of Origin before your changes are merged. This can be done by adding Signed-off-by: John Doe <john.doe@email.org> to the last line of each Git commit message. The e-mail address used to sign must match the e-mail address of the Git author. Click here to view the Developer Certificate of Origin agreement.

• Commit 8969aa5 must be signed by lehoainham@gmail.com

[vmwclabot]

@nhamlh, you must sign every commit in this pull request acknowledging our Developer Certificate of Origin before your changes are merged. This can be done by adding Signed-off-by: John Doe <john.doe@email.org> to the last line of each Git commit message. The e-mail address used to sign must match the e-mail address of the Git author. Click here to view the Developer Certificate of Origin agreement.

• Commit 2f49a0a must be signed by dbrian@vmware.com

[slimm609]

DCO was removed due to github rebase. bypassing since it was signed above