[vm/sigprof] Disable checking of sigprof on mac.
[vm/sigprof] Disable checking of sigprof on mac.

Fixes https://github.com/dart-lang/sdk/issues/41239

Change-Id: I397f70c7d9977bbf8ce33ce649c7d82e02fd26a7
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/151880
Reviewed-by: Ryan Macnak <d738b7f001baf9789095d7dc549cff6de60b011d@google.com>
Commit-Queue: Alexander Aprelev <dfb74c35a357c2059971a4bf7fe26b6a7c18085d@google.com>

dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk