cmake build system: detect clang if it is simply a c++ symlink

Signed-off-by: Tim Blechmann <tim@Tims-MacBook-Pro.local>
osx: disable WII support by default

Signed-off-by: Tim Blechmann <tim@klingt.org>
sclang: avoid preprocessor warning

Signed-off-by: Tim Blechmann <tim@klingt.org>
scide: avoid clang warning

Signed-off-by: Tim Blechmann <tim@klingt.org>