AK: Define FloatExtractor for long double when it's an alias of double

On some platforms, like macOS on ARM, long double is a different type
but has the exact same characteristics as a normal double. When it is
the case, define FloatExtractor<long double> as an alias to
FloatExtractor<double>.

AK/FloatingPoint.h

@@ -87,6 +87,13 @@ struct FloatExtractor<f64> {
 };
 static_assert(AssertSize<FloatExtractor<f64>, sizeof(f64)>());
 
+#ifdef AK_LONG_DOUBLE_IS_DOUBLE
+template<>
+struct FloatExtractor<long double> : FloatExtractor<double> {
+};
+static_assert(AssertSize<FloatExtractor<long double>, sizeof(FloatExtractor<double>)>());
+#endif
+
 template<>
 struct FloatExtractor<f32> {
     static constexpr FloatExtractor<f32> from_float(f32 f) { return bit_cast<FloatExtractor<f32>>(f); }

AK/Types.h

@@ -30,6 +30,8 @@ using f80 = long double;
 #    elif __LDBL_MANT_DIG__ == 113 && __LDBL_MAX_EXP__ == 16384
 #        define AK_HAS_FLOAT_128 1
 using f128 = long double;
+#    elif __LDBL_MANT_DIG__ == __DBL_MANT_DIG__ && __LDBL_MAX_EXP__ == __DBL_MAX_EXP__
+#        define AK_LONG_DOUBLE_IS_DOUBLE
 #    endif
 #endif