SSE4.2 assertion

[ksmk]

there's a problem with SSE assertion ( clang-3.6, i7 gulftown)

App.cpp:178:6: error: use of
undeclared identifier '__builtin_cpu_supports'
if(!__builtin_cpu_supports("sse4.2"))
^
1 error generated.

[Panagiotis Christopoulos Charitos]

There is an assumption in AnKi that clang is GCC compatible. __builtin_cpu_supports is supported in clang 3.7. What I'll do is to bump the clang required version in the README.txt to 3.7.

Thanks for your report!