In Metadata.h/.cpp, start building the relative wtable support even on platforms that don't use it yet (#64354)

Author: kubamracek

include/swift/Runtime/Metadata.h

@@ -369,13 +369,11 @@ swift_getWitnessTable(const ProtocolConformanceDescriptor *conformance,
                       const Metadata *type,
                       const void * const *instantiationArgs);
 
-#if SWIFT_STDLIB_USE_RELATIVE_PROTOCOL_WITNESS_TABLES
 SWIFT_RUNTIME_EXPORT
 const RelativeWitnessTable *
 swift_getWitnessTableRelative(const ProtocolConformanceDescriptor *conformance,
                       const Metadata *type,
                       const void * const *instantiationArgs);
-#endif
 
 /// Retrieve an associated type witness from the given witness table.
 ///
@@ -392,15 +390,13 @@ MetadataResponse swift_getAssociatedTypeWitness(
                                           const Metadata *conformingType,
                                           const ProtocolRequirement *reqBase,
                                           const ProtocolRequirement *assocType);
-#if SWIFT_STDLIB_USE_RELATIVE_PROTOCOL_WITNESS_TABLES
 SWIFT_RUNTIME_EXPORT SWIFT_CC(swift)
 MetadataResponse swift_getAssociatedTypeWitnessRelative(
                                           MetadataRequest request,
                                           RelativeWitnessTable *wtable,
                                           const Metadata *conformingType,
                                           const ProtocolRequirement *reqBase,
                                           const ProtocolRequirement *assocType);
-#endif
 /// Retrieve an associated conformance witness table from the given witness
 /// table.
 ///
@@ -419,15 +415,13 @@ const WitnessTable *swift_getAssociatedConformanceWitness(
                                   const ProtocolRequirement *reqBase,
                                   const ProtocolRequirement *assocConformance);
 
-#if SWIFT_STDLIB_USE_RELATIVE_PROTOCOL_WITNESS_TABLES
 SWIFT_RUNTIME_EXPORT SWIFT_CC(swift)
 const RelativeWitnessTable *swift_getAssociatedConformanceWitnessRelative(
                                   RelativeWitnessTable *wtable,
                                   const Metadata *conformingType,
                                   const Metadata *assocType,
                                   const ProtocolRequirement *reqBase,
                                   const ProtocolRequirement *assocConformance);
-#endif
 
 /// Determine whether two protocol conformance descriptors describe the same
 /// conformance of a type to a protocol.

stdlib/public/runtime/Metadata.cpp

@@ -5689,7 +5689,6 @@ swift::swift_getWitnessTable(const ProtocolConformanceDescriptor *conformance,
   return uniqueForeignWitnessTableRef(result.second);
 }
 
-#if SWIFT_STDLIB_USE_RELATIVE_PROTOCOL_WITNESS_TABLES
 namespace {
 
 /// A cache-entry type suitable for use with LockingConcurrentMap.
@@ -5987,7 +5986,6 @@ swift::swift_getWitnessTableRelative(const ProtocolConformanceDescriptor *confor
   return reinterpret_cast<RelativeWitnessTable*>(((uintptr_t)table) |
                                                  (uintptr_t)0x1);
 }
-#endif
 
 /// Find the name of the associated type with the given descriptor.
 static StringRef findAssociatedTypeName(const ProtocolDescriptor *protocol,
@@ -6209,7 +6207,6 @@ RelativeWitnessTable *swift::lookThroughOptionalConditionalWitnessTable(
   return table;
 }
 
-#if SWIFT_STDLIB_USE_RELATIVE_PROTOCOL_WITNESS_TABLES
 SWIFT_CC(swift)
 static MetadataResponse
 swift_getAssociatedTypeWitnessRelativeSlowImpl(
@@ -6307,7 +6304,6 @@ swift::swift_getAssociatedTypeWitnessRelative(MetadataRequest request,
                                                     conformingType, reqBase,
                                                     assocType);
 }
-#endif
 
 using AssociatedConformanceWitness = std::atomic<void *>;
 
@@ -6452,7 +6448,6 @@ const WitnessTable *swift::swift_getAssociatedConformanceWitness(
                                                    assocConformance);
 }
 
-#if SWIFT_STDLIB_USE_RELATIVE_PROTOCOL_WITNESS_TABLES
 SWIFT_CC(swift)
 static const RelativeWitnessTable *swift_getAssociatedConformanceWitnessRelativeSlowImpl(
                                   RelativeWitnessTable *wtable,
@@ -6541,7 +6536,6 @@ const RelativeWitnessTable *swift::swift_getAssociatedConformanceWitnessRelative
                                                    assocType, reqBase,
                                                    assocConformance);
 }
-#endif
 
 bool swift::swift_compareProtocolConformanceDescriptors(
     const ProtocolConformanceDescriptor *lhs,