[Reflection] Fix build breakage caused by wrong type argument.

The discriminator argument to int_ptrauth_sign needs to be an Builtin.Int64,
not a UInt64.

rdar://106138642

Author: al45tair

stdlib/public/Reflection/Sources/_Runtime/Utils/PtrAuth.swift

@@ -200,7 +200,7 @@ extension PtrAuth {
       Key.processIndependentCode._value,
       UInt64(Builtin.typePtrAuthDiscriminator(
         Metadata.AccessFunction.AccessFn0.self
-      ))
+      )._value)
     ))
 
     return signedBitPattern.rawPointer
@@ -214,7 +214,7 @@ extension PtrAuth {
       Key.processIndependentCode._value,
       UInt64(Builtin.typePtrAuthDiscriminator(
         Metadata.AccessFunction.AccessFn1.self
-      ))
+      )._value)
     ))
 
     return signedBitPattern.rawPointer
@@ -228,7 +228,7 @@ extension PtrAuth {
       Key.processIndependentCode._value,
       UInt64(Builtin.typePtrAuthDiscriminator(
         Metadata.AccessFunction.AccessFn2.self
-      ))
+      )._value)
     ))
 
     return signedBitPattern.rawPointer
@@ -242,7 +242,7 @@ extension PtrAuth {
       Key.processIndependentCode._value,
       UInt64(Builtin.typePtrAuthDiscriminator(
         Metadata.AccessFunction.AccessFn3.self
-      ))
+      )._value)
     ))
 
     return signedBitPattern.rawPointer
@@ -256,7 +256,7 @@ extension PtrAuth {
       Key.processIndependentCode._value,
       UInt64(Builtin.typePtrAuthDiscriminator(
         Metadata.AccessFunction.AccessFnMany.self
-      ))
+      )._value)
     ))
 
     return signedBitPattern.rawPointer