Fix fuzzer build failure (#7739)

Author: var-const

Firestore/core/CMakeLists.txt

@@ -136,6 +136,7 @@ target_link_libraries(
   absl_meta
   absl_optional
   absl_strings
+  absl::time
 )
 
 if(HAVE_OPENSSL_RAND_H)

Firestore/fuzzing/CMakeLists.txt

@@ -32,7 +32,7 @@ set(
   ${FIREBASE_SOURCE_DIR}/Firestore/Example/FuzzTests/FuzzingResources
 )
 
-link_libraries(firestore_core)
+link_libraries(firestore_core firestore_util)
 
 
 # Serializer fuzzing target.

Firestore/fuzzing/serializer_fuzzer.cc

@@ -22,20 +22,23 @@
 #include "Firestore/core/src/nanopb/message.h"
 #include "Firestore/core/src/nanopb/reader.h"
 #include "Firestore/core/src/remote/serializer.h"
+#include "Firestore/core/src/util/read_context.h"
 
 using firebase::firestore::google_firestore_v1_Value;
 using firebase::firestore::model::DatabaseId;
 using firebase::firestore::nanopb::Message;
 using firebase::firestore::nanopb::StringReader;
 using firebase::firestore::remote::Serializer;
+using firebase::firestore::util::ReadContext;
 
 extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size) {
   Serializer serializer{DatabaseId{"project", DatabaseId::kDefault}};
   try {
     // Try to decode the received data using the serializer.
     StringReader reader{data, size};
     auto message = Message<google_firestore_v1_Value>::TryParse(&reader);
-    serializer.DecodeFieldValue(&reader, *message);
+    ReadContext context;
+    serializer.DecodeFieldValue(&context, *message);
   } catch (...) {
     // Ignore caught errors and assertions because fuzz testing is looking for
     // crashes and memory errors.