Remove relaxed add/mul for Float16 on wasm, as they cannot be defined.

Author: stephentyrone

Sources/RealModule/Float16+Real.swift

@@ -173,6 +173,10 @@ extension Float16: Real {
   }
   #endif
 
+  #if !arch(wasm32)
+  // WASM doesn't have _Float16 on the C side, so we can't define the C hooks
+  // that these use. TODO: implement these as Swift builtins instead.
+  
   @_transparent
   public static func _relaxedAdd(_ a: Float16, _ b: Float16) -> Float16 {
     _numerics_relaxed_addf16(a, b)
@@ -182,6 +186,7 @@ extension Float16: Real {
   public static func _relaxedMul(_ a: Float16, _ b: Float16) -> Float16 {
     _numerics_relaxed_mulf16(a, b)
   }
+  #endif
 }
 
 #endif