Exclude sub-packages of abseil that are problematic (#2597)

Author: wilhuff

FirebaseFirestore.podspec

@@ -95,10 +95,19 @@ Google Cloud Firestore is a NoSQL document database built for automatic scaling,
       'Firestore/third_party/abseil-cpp/**/*.cc'
     ]
     ss.exclude_files = [
+      # Exclude tests and benchmarks from the framework.
       'Firestore/third_party/abseil-cpp/**/*_benchmark.cc',
       'Firestore/third_party/abseil-cpp/**/*test*.cc',
       'Firestore/third_party/abseil-cpp/absl/hash/internal/print_hash_of.cc',
-      'Firestore/third_party/abseil-cpp/absl/synchronization/internal/mutex_nonprod.cc',
+
+      # Avoid the debugging package which uses code that isn't portable to
+      # ARM (see stack_consumption.cc) and uses syscalls not available on
+      # tvOS (e.g. sigaltstack).
+      'Firestore/third_party/abseil-cpp/absl/debugging/**/*.cc',
+
+      # Exclude the synchronization package because it's dead weight: we don't
+      # write the kind of heavily threaded code that might benefit from it.
+      'Firestore/third_party/abseil-cpp/absl/synchronization/**/*.cc',
     ]
 
     ss.library = 'c++'