chore: import upstream snapshot with attribution

cmake/checks/cpu_ssse3.cpp

@@ -0,0 +1,7 @@
+#include <tmmintrin.h>
+const double v = 0;
+int main() {
+    __m128i a = _mm_setzero_si128();
+    __m128i b = _mm_abs_epi32(a);
+    return 0;
+}