Return the minimal alignment required by the platform ABI for values of the given
type. The address of a variable or struct member of the given type must always be
a multiple of this alignment. For example, most platforms require int variables
to be aligned at a 4-byte boundary, so
G_ALIGNOF (int) is 4 on most platforms.
Note this is not necessarily the same as the value returned by GCC’s
__alignof__ operator, which returns the preferred alignment for a type.
The preferred alignment may be a stricter alignment than the minimal alignment.