clang-cl.exe defines __clang__ and _MSC_VER but not __GNUC__, so a clang-
specific guard is needed to get the correct ALIGNxx versions.
Fixes#21914
Change-Id: Icdc047b182ad1ba61c7b1b06a1e951eda1a0c33d
Reviewed-by: Hugo Landau <hlandau@openssl.org>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
Reviewed-by: Paul Dale <pauli@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/21921)