compiler: do not allow expansion-to-defined

'-Wexpansion-to-defined'
     Warn whenever 'defined' is encountered in the expansion of a macro
     (including the case where the macro is expanded by an '#if'
     directive).  Such usage is not portable.  This warning is also
     enabled by '-Wpedantic' and '-Wextra'.

This is enabled by default in llvm but not in gcc. Given that it is 'not
portable', lets disallow this in gcc and keep both compilers in sync.

Signed-off-by: Anas Nashif <anas.nashif@intel.com>