Runtime: share the visibility types

Use the common definitions rather than redefining macros everywhere.
Centralise the type declarations in `Types.h`.

Author: compnerd

Sources/Runtime/KnownMetadata.c

@@ -2,34 +2,23 @@
 // All Rights Reserved.
 // SPDX-License-Identifier: BSD-3
 
-#if defined(__ELF__)
-#define SWIFT_RUNTIME_ABI __attribute__((__visibility__("default")))
-#elif defined(__MACH__)
-#define SWIFT_RUNTIME_ABI __attribute__((__visibility__("default")))
-#elif defined(__WASM__)
-#define SWIFT_RUNTIME_ABI __attribute__((__visibility__("default")))
-#else
-#define SWIFT_RUNTIME_ABI __declspec(dllexport)
-#endif
-
-struct ValueWitnessTable {};
-
-struct TypeMetadata {};
+#include "Types.h"
+#include "Visibility.h"
 
 SWIFT_RUNTIME_ABI
-struct ValueWitnessTable $sBi8_WV;
+ValueWitnessTable $sBi8_WV;
 
 SWIFT_RUNTIME_ABI
-struct ValueWitnessTable $sBi32_WV;
+ValueWitnessTable $sBi32_WV;
 
 SWIFT_RUNTIME_ABI
-struct ValueWitnessTable $sytWV;
+ValueWitnessTable $sytWV;
 
 SWIFT_RUNTIME_ABI
-struct TypeMetadata $sBi1_N;
+TypeMetadata $sBi1_N;
 
 SWIFT_RUNTIME_ABI
-struct TypeMetadata $sBi8_N;
+TypeMetadata $sBi8_N;
 
 SWIFT_RUNTIME_ABI
-struct TypeMetadata $sBi32_N;
+TypeMetadata $sBi32_N;

Sources/Runtime/Types.h

@@ -6,26 +6,31 @@
 #define uSwift_Runtime_Types_h
 
 typedef struct Metadata Metadata;
-typedef struct EnumMetadata EnumMetadata;
-typedef struct ValueMetadata ValueMetadata;
 typedef struct OpaqueValue OpaqueValue;
 
-typedef struct ValueTypeDescriptor ValueTypeDescriptor;
+typedef enum EnumLayoutFlags {
+  invalid,
+} EnumLayoutFlags;
+typedef struct EnumMetadata EnumMetadata;
+
 typedef struct GenericValueMetadataPattern GenericValueMetadataPattern;
 
+typedef struct HeapObject HeapObject;
+
 typedef struct MetdataRequest {
 } MetadataRequest;
 typedef struct MetdataResponse {
 } MetadataResponse;
 
 typedef struct TypeContextDescriptor TypeContextDescriptor;
 typedef struct TypeLayout TypeLayout;
+typedef struct TypeMetadata {
+} TypeMetadata;
 
-typedef struct HeapObject HeapObject;
-
-typedef enum EnumLayoutFlags {
-  invalid,
-} EnumLayoutFlags;
+typedef struct ValueMetadata ValueMetadata;
+typedef struct ValueTypeDescriptor ValueTypeDescriptor;
+typedef struct ValueWitnessTable {
+} ValueWitnessTable;
 
 typedef void(__attribute__((__swiftcall__)) *
              StoreExtraInhabitantTagFn)(OpaqueValue *value, unsigned store_case,