chore: import upstream snapshot with attribution

cmake/checks/cpu_sse3.cpp

@@ -0,0 +1,7 @@
+#include <pmmintrin.h>
+int main() {
+    __m128 u, v;
+    u = _mm_set1_ps(0.0f);
+    v = _mm_moveldup_ps(u); // SSE3
+    return 0;
+}