Thomas temby/fix sign pipeline

[thomas-temby]

Description

Mandatory Checklist

• Please choose the target release of Azure PowerShell. (⚠️Target release is a different concept from API readiness. Please click below links for details.)

  • General release
  • Public preview
  • Private preview
  • Engineering build
  • No need for a release

• Check this box to confirm: I have read the Submitting Changes section of CONTRIBUTING.md and reviewed the following information:

• SHOULD update ChangeLog.md file(s) appropriately
  • Update src/{{SERVICE}}/{{SERVICE}}/ChangeLog.md.
    • A snippet outlining the change(s) made in the PR should be written under the ## Upcoming Release header in the past tense.
  • Should not change ChangeLog.md if no new release is required, such as fixing test case only.
• SHOULD regenerate markdown help files if there is cmdlet API change. Instruction
• SHOULD have proper test coverage for changes in pull request.
• SHOULD NOT adjust version of module manually in pull request

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[Copilot]

Pull request overview

Updates the MSI generation script used by the Azure PowerShell installer packaging flow to support building in environments where Windows Installer ICE validation can’t run (e.g., containerized builds), while keeping existing validation behavior by default.

Changes:

• Adds an AZPS_SKIP_MSI_ICE_VALIDATION environment-variable switch to control whether WiX light runs ICE validation.
• When the switch is enabled ('true'), passes -sval to light to suppress validation; otherwise retains the prior behavior (-sice:ICE80).