Increase default timeout to 75 minutes for windows_arm64 build

[Copilot]

windows_arm64 agents are slower than other platforms, causing stress/diagnostic pipeline jobs (jitstress, gcstress, superpmi, pgo, ilasm, etc.) to hit the default 60-minute ADO job timeout and Build fails.

All windows_arm64 jobs fan out through a single block in eng/pipelines/common/platform-matrix.yml, so one targeted change covers all affected pipelines.

Change

In the windows_arm64 block of platform-matrix.yml, inject timeoutInMinutes: 75 as a default — but only when the caller hasn't already supplied its own value:

jobParameters:
  runtimeFlavor: ${{ parameters.runtimeFlavor }}
  buildConfig: ${{ parameters.buildConfig }}
  helixQueueGroup: ${{ parameters.helixQueueGroup }}
  # windows_arm64 agents are slower; give a larger default timeout,
  # but only when the calling pipeline hasn't specified its own.
  ${{ if eq(parameters.jobParameters.timeoutInMinutes, '') }}:
    timeoutInMinutes: 75
  ${{ insert }}: ${{ parameters.jobParameters }}

The guard eq(parameters.jobParameters.timeoutInMinutes, '') is used instead of containsValue (which inspects values, not keys). When a caller like libraries-jitstress*.yml already passes timeoutInMinutes: 360, the guard is false and the default is suppressed — no duplicate-key error, and the existing 360 is preserved via ${{ insert }}.

All other platform blocks (windows_x64, windows_x86, linux_, osx_) are untouched.

[dotnet-policy-service]

Tagging subscribers to this area: @JulieLeeMSFT, @jakobbotsch
See info in area-owners.md if you want to be subscribed.

[JulieLeeMSFT]

windows arm64 builds for ~10 pipelines have been timing out since end of May. Probably the build time increase from < 50min to > 50 min started when we started to build wasm. Increasing the timeout to 75min.
@dotnet/jit-contrib, PTAL.

[Copilot]

Pull request overview

This PR attempts to raise the default Azure Pipelines job timeout for the windows_arm64 platform fan-out in eng/pipelines/common/platform-matrix.yml (to reduce windows_arm64 job timeouts across multiple pipelines).

Changes:

• Adds a conditional default timeoutInMinutes: 75 injection in the windows_arm64 jobParameters block when the caller has not supplied a timeout.