common.h: Prevent error when compiling with Clang

[nishalkulkarni]

Clang requires fields to have a constant size and does not support variable length array in structure causing build to to fail at compile_check()

error: fields must have a constant size: 'variable length array in structure' extension will never be supported

This change selects the compatible version of ALIGN_UP and ALIGN_DOWN macro when compiling with Clang.

While there's no official support for LLVM toolchain right now, this change should help in that direction.

[sofci]

Can one of the admins verify this patch?

reply test this please to run this test once

[sys-pt1s]

Can one of the admins verify this patch?

[lgirdwood]

test this please

[kv2019i]

@wszypelt This one got stuck as well.

[lgirdwood]

@wszypelt @lrudyX good to merge ?

[wszypelt]

@lgirdwood good to merge

[kv2019i]

Test infra issue in https://sof-ci.01.org/sofpr/PR7411/build5584/devicetest/index.html , not blocking this PR.

[marc-hb]

Which clang version does this solve a problem with? We've been routinely using xt-clang for a while now and this has never been an issue: https://sof-ci.01.org/sofpr/PR7411/build5583/build/mtl_zph_ipc4.txt

-- The C compiler identification is Clang 10.0.1
-- The CXX compiler identification is Clang 10.0.1

[marc-hb]

Oh wait, I suspect xt-clang defines BOTH __XCC__ and __clang__, that would explain why we didn't hit this issue.

@dcpleung should this be changed to ! GCC or something?

More background:

• compile: restore alignment checks for some cases of ALIGN() #3804