cmake - intinsics fixes, only compile SSE source with SSE flags on non-windows...

cmake - intinsics fixes, only compile SSE source with SSE flags on non-windows when target use runtime check (GH #154). For windows we only use /arch flag when target is presumed to support SSE to avoid AVX function pollution (GH #132).

Signed-off-by: Jean-Marc Valin <jmvalin@jmvalin.ca>