compileroptions.cmake: fixed workaround for Clang >= 14

[firewave]

This fixes commit a586b9e.

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This cannot be checked for and thus is never applied:

-- Performing Test HAS_CXX_FLAG_mllvm
-- Performing Test HAS_CXX_FLAG_mllvm - Failed

There's also a version check before this option is being used so this should always be safe.

CC @pfultz2

[danmar]

I have no opinion

[pfultz2]

There's also a version check before this option is being used so this should always be safe.

It wont always be safe. Some variants of clang report version 14 but do not support this flag. I ran into this very issue which is why I changed it.

I think we can put quotes around it to check for multiple flags together with check_cxx_compiler_flag, so we may need to just use this function directly.

[firewave]

There's also a version check before this option is being used so this should always be safe.

It wont always be safe. Some variants of clang report version 14 but do not support this flag. I ran into this very issue which is why I changed it.

Which variants? I would assume that it is AppleClang or a pre-release version.

I think we can put quotes around it to check for multiple flags together with check_cxx_compiler_flag, so we may need to just use this function directly.

I will give that a try.

[pfultz2]

I would assume that it is AppleClang or a pre-release version.

Its the clang provided by rocm.

[firewave]

I think we can put quotes around it to check for multiple flags together with check_cxx_compiler_flag, so we may need to just use this function directly.

That seems to do the trick.

[firewave]

That makes the check pass but it probably passes the two arguments as a single one because of the quotes which leads to the failure. I locally confirmed that Clang 14 and 15 support those options.

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Our helper simply doesn't work with this. Using a custom check will obviously work.

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On a side note in future versions of Clang the option can be specified without a space via -mllvm= - see llvm/llvm-project@90094ab.

[firewave]

@pfultz2 Does this work for you?

Something off-topic. If you guys approve each others PRs I am comfortable to merge stuff even if I don't understand what it is doing.

[pfultz2]

LGTM