cmake: support multiple CPU targets

cmake/checks/cpu_avx.cpp

@@ -0,0 +1,9 @@
+#if !defined __AVX__ // MSVC supports this flag since MSVS 2013
+#error "__AVX__ define is missing"
+#endif
+#include <immintrin.h>
+void test()
+{
+    __m256 a = _mm256_set1_ps(0.0f);
+}
+int main() { return 0; }