devkit: add RHEL support to patch and fix uname

[sxa]

Part of adoptium/temurin-build#3749

Notes:

• This allows 'RHEL' to be used as the OS name, and will download the packages on-demand. This requires yum-utils to be installed (infrastructure PR) unlike the previous solution (which required them to have been pre-downloaded by an administrator on the machine.
• The version number you specify to the script is irrelevant - it will only create a devkit for the RHEL version that's being used

[github-actions]

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[gdams]

Out of interest are we upstreaming these patches for consistency?