build: Add compiler version checking for Clang

[andreittr]

Description of changes

This change adds version checking make functions in line with what we have already for GCC.
Also added are *_lt functions that check for a maximum compiler version.

Prerequisite checklist

• Read the contribution guidelines regarding submitting new changes to the project;
• Tested your changes against relevant architectures and platforms;
• Ran the checkpatch.uk on your commit series before opening this PR;
• Updated relevant documentation.

Base target

• Architecture(s): N/A
• Platform(s): N/A
• Application(s): N/A

Additional configuration

N/A

Edit: rebased & addressed comments.

[StefanJum]

@andreittr I think this will be covered by #944

[unikraft-bot]

✅ Checkpatch passed

Beep boop! I ran Unikraft's checkpatch.pl support script on your pull request and it all looks good!

SHA	commit	checkpatch
9ed8da6	build: Add compiler version checking for clang	✅

[razvand]

Hi, @andreittr . This looks good. My only comment would be using capitalized Clang in your commit message.

[StefanJum]

@razvand do we go for this and have #944 rebased on top?
The compiler version checking is also done by that one (see the comment above).

[razvand]

@StefanJum , yes, it makes sense. Let's merge this and then have #944 rebased on top of this.

[StefanJum]

@andreittr can you please also add a error_if_clang_version_lt, similar to what we have for gcc?

[razvand]

Reviewed-by: Razvan Deaconescu razvand@unikraft.io
Approved-by: Razvan Deaconescu razvand@unikraft.io