yaml: Fix compilation in cygwin

Author: Yankes

libs/rapidyaml/c4/ext/fast_float_all.h

@@ -416,7 +416,7 @@ value128 full_multiplication(uint64_t a, uint64_t b) {
   // But MinGW on ARM64 doesn't have native support for 64-bit multiplications
   answer.high = __umulh(a, b);
   answer.low = a * b;
-#elif defined(FASTFLOAT_32BIT) || (defined(_WIN64) && !defined(__clang__))
+#elif defined(FASTFLOAT_32BIT) || (defined(_WIN64) && !defined(__clang__) && !defined(__CYGWIN__))
   answer.low = _umul128(a, b, &answer.high); // _umul128 not available on ARM64
 #elif defined(FASTFLOAT_64BIT) && defined(__SIZEOF_INT128__)
   __uint128_t r = ((__uint128_t)a) * b;