Arm backend: Refactor check_platform_support

[perheld]

Move check_platform_support() to utils.sh file since it will be used by other scripts in coming commits.

Add check_os_support() in utils.sh and call it from main.

Change-Id: Ia9da3ece1e3f561a042f6796c0741f97b11c6f4c
Signed-off-by: per.held@arm.com

[pytorch-bot]

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