[ObjC] Add PROTOC_EXPORT for the CMake unittest build/link.

These aren't public api, but this is currently need for how the CMake build is
configured.

src/google/protobuf/compiler/objectivec/generator.h

@@ -37,9 +37,8 @@
 #include "google/protobuf/compiler/code_generator.h"
 #include "google/protobuf/descriptor.h"
 
-// clang-format off
+// Must be included last
 #include "google/protobuf/port_def.inc"
-// clang-format on
 
 namespace google {
 namespace protobuf {

src/google/protobuf/compiler/objectivec/line_consumer.h

@@ -36,31 +36,39 @@
 
 #include "google/protobuf/io/zero_copy_stream.h"
 
+// Must be included last
+#include "google/protobuf/port_def.inc"
+
 namespace google {
 namespace protobuf {
 namespace compiler {
 namespace objectivec {
 
+// TODO(b/250947994): PROTOC_EXPORT is only used to allow the CMake build to
+// find/link these in the unittest, this is not public api.
+
 // Helper for parsing simple files.
-class LineConsumer {
+class PROTOC_EXPORT LineConsumer {
  public:
   LineConsumer();
   virtual ~LineConsumer();
   virtual bool ConsumeLine(const absl::string_view& line, std::string* out_error) = 0;
 };
 
-bool ParseSimpleFile(const std::string& path,
-                     LineConsumer* line_consumer,
-                     std::string* out_error);
+bool PROTOC_EXPORT ParseSimpleFile(const std::string& path,
+                                   LineConsumer* line_consumer,
+                                   std::string* out_error);
 
-bool ParseSimpleStream(io::ZeroCopyInputStream& input_stream,
-                       const std::string& stream_name,
-                       LineConsumer* line_consumer,
-                       std::string* out_error);
+bool PROTOC_EXPORT ParseSimpleStream(io::ZeroCopyInputStream& input_stream,
+                                     const std::string& stream_name,
+                                     LineConsumer* line_consumer,
+                                     std::string* out_error);
 
 }  // namespace objectivec
 }  // namespace compiler
 }  // namespace protobuf
 }  // namespace google
 
+#include "google/protobuf/port_undef.inc"
+
 #endif  // GOOGLE_PROTOBUF_COMPILER_OBJECTIVEC_LINE_CONSUMER_H__

src/google/protobuf/compiler/objectivec/names.h

@@ -39,9 +39,8 @@
 #include "google/protobuf/descriptor.h"
 #include "google/protobuf/io/zero_copy_stream.h"
 
-// clang-format off
+// Must be included last
 #include "google/protobuf/port_def.inc"
-// clang-format on
 
 namespace google {
 namespace protobuf {

src/google/protobuf/compiler/objectivec/text_format_decode_data.h

@@ -34,14 +34,20 @@
 #include <string>
 #include <vector>
 
+// Must be included last
+#include "google/protobuf/port_def.inc"
+
 namespace google {
 namespace protobuf {
 namespace compiler {
 namespace objectivec {
 
+// TODO(b/250947994): PROTOC_EXPORT is only used to allow the CMake build to
+// find/link these in the unittest, this is not public api.
+
 // Generate decode data needed for ObjC's GPBDecodeTextFormatName() to transform
 // the input into the expected output.
-class TextFormatDecodeData {
+class PROTOC_EXPORT TextFormatDecodeData {
  public:
   TextFormatDecodeData();
   ~TextFormatDecodeData();
@@ -68,4 +74,6 @@ class TextFormatDecodeData {
 }  // namespace protobuf
 }  // namespace google
 
+#include "google/protobuf/port_undef.inc"
+
 #endif  // GOOGLE_PROTOBUF_COMPILER_OBJECTIVEC_TEXT_FORMAT_DECODE_DATA_H__