client almost builds

vendor/cryptopp/TestPrograms/test_x86_avx2.cpp

@@ -0,0 +1,9 @@
+#include <immintrin.h>
+int main(int argc, char* argv[])
+{
+    // _mm256_broadcastsi128_si256 due to Clang
+    __m128i x = _mm_setzero_si128 ();
+    __m256i y = _mm256_broadcastsi128_si256 (x);
+    y = _mm256_add_epi64 (y,y);
+    return 0;
+}