Fix RCT-Folly build error when use_frameworks! and hermes are both en…

…abled (facebook#34030)

Summary:
This PR is fixing the build errors on iOS when `use_frameworks!` and `:hermes_enabled` are both enabled. There are two errors:

- fmt/compile.h include not found: This PR adds fmt in header search paths.
- undefined symbols `_jump_fcontext` and `_make_fcontext` from boost. the two symbols are actually not be unused. because to generate the shared library in dynamic framework mode, LTO (Link-Time-Optimization) is not as powerful as generating a single executable.

## Changelog

[iOS] [Fixed] - Fix RCT-Folly build error when use_frameworks! and hermes are both enabled

Pull Request resolved: facebook#34030

Test Plan:
- CI passed

-
```
$ npx react-native init RN069 --version next
# edit RN069/ios/Podfile to enable use_frameworks! and hermes_enabled
# patch node_modules/react-native from both facebook#34011 and this prs' patch
$ pod install
$ yarn ios
```

Reviewed By: cortinico

Differential Revision: D37284084

Pulled By: dmitryrykun

fbshipit-source-id: 923fa03d7844d1d227880919c8b2c8614c848d59

third-party-podspecs/RCT-Folly.podspec

@@ -75,7 +75,10 @@ Pod::Spec.new do |spec|
   spec.libraries           = "c++abi" # NOTE Apple-only: Keep c++abi here due to https://github.com/react-native-community/releases/issues/251
   spec.pod_target_xcconfig = { "USE_HEADERMAP" => "NO",
                                "CLANG_CXX_LANGUAGE_STANDARD" => "c++17",
-                               "HEADER_SEARCH_PATHS" => "\"$(PODS_TARGET_SRCROOT)\" \"$(PODS_ROOT)/boost\" \"$(PODS_ROOT)/DoubleConversion\" \"$(PODS_ROOT)/libevent/include/\"" }
+                               "HEADER_SEARCH_PATHS" => "\"$(PODS_TARGET_SRCROOT)\" \"$(PODS_ROOT)/boost\" \"$(PODS_ROOT)/DoubleConversion\" \"$(PODS_ROOT)/libevent/include/\" \"$(PODS_ROOT)/fmt/include\"",
+                               # In dynamic framework (use_frameworks!) mode, ignore the unused and undefined boost symbols when generating the library.
+                               "OTHER_LDFLAGS" => "\"-Wl,-U,_jump_fcontext\" \"-Wl,-U,_make_fcontext\""
+                             }
 
   # TODO: The boost spec should really be selecting these files so that dependents of Folly can also access the required headers.
   spec.user_target_xcconfig = { "HEADER_SEARCH_PATHS" => "\"$(PODS_ROOT)/boost\"" }