Workaround for __BIGGEST_ALIGNMENT__ on Clang
On x86_64,__BIGGEST_ALIGNMENT__
is always 128 bits, rendering it incompatible with AVX.
GCC reports the maximum enabled vector width (which is what we want) and Intel reports the maximum supported vector width (which is okay too).
Reported by @RudolfWeeber. Corresponding LLVM bug report at https://bugs.llvm.org/show_bug.cgi?id=42554.
Edited by Michael Kuron