Fix the compiler flags for libraries (#43071)

Summary:
While looking at another issue, I realized that in some cases the script was adding the same flags twice and it was leaving the RCT_NEW_ARCH_ENABLED behind.

## Changelog:
[iOS][Fixed] - Pass the right flags to libraries

Pull Request resolved: #43071

Test Plan: Fixed Unit tests

Reviewed By: huntie

Differential Revision: D53860576

Pulled By: cipolleschi

fbshipit-source-id: 1f6f4852df8d316293b93d7c5fbef09a249893a5

packages/react-native/scripts/cocoapods/__tests__/new_architecture-test.rb

@@ -150,7 +150,7 @@ def test_installModulesDependencies_whenNewArchEnabledAndNewArchAndNoSearchPaths
         folly_config = Helpers::Constants.folly_config
         folly_compiler_flags = folly_config[:compiler_flags]
 
-        assert_equal(spec.compiler_flags, NewArchitectureHelper.folly_compiler_flags)
+        assert_equal(spec.compiler_flags, "-DRCT_NEW_ARCH_ENABLED=1 #{NewArchitectureHelper.folly_compiler_flags}")
         assert_equal(spec.pod_target_xcconfig["HEADER_SEARCH_PATHS"], "\"$(PODS_ROOT)/boost\" \"$(PODS_ROOT)/Headers/Private/Yoga\" \"$(PODS_ROOT)/DoubleConversion\" \"$(PODS_ROOT)/fmt/include\" \"${PODS_CONFIGURATION_BUILD_DIR}/React-graphics/React_graphics.framework/Headers\" \"${PODS_CONFIGURATION_BUILD_DIR}/React-graphics/React_graphics.framework/Headers/react/renderer/graphics/platform/ios\" \"${PODS_CONFIGURATION_BUILD_DIR}/React-Fabric/React_Fabric.framework/Headers\" \"${PODS_CONFIGURATION_BUILD_DIR}/React-Fabric/React_Fabric.framework/Headers/react/renderer/components/view/platform/cxx\" \"${PODS_CONFIGURATION_BUILD_DIR}/React-FabricImage/React_FabricImage.framework/Headers\" \"${PODS_CONFIGURATION_BUILD_DIR}/ReactCommon/ReactCommon.framework/Headers\" \"${PODS_CONFIGURATION_BUILD_DIR}/ReactCommon/ReactCommon.framework/Headers/react/nativemodule/core\" \"${PODS_CONFIGURATION_BUILD_DIR}/React-NativeModulesApple/React_NativeModulesApple.framework/Headers\" \"${PODS_CONFIGURATION_BUILD_DIR}/React-RCTFabric/RCTFabric.framework/Headers\" \"${PODS_CONFIGURATION_BUILD_DIR}/React-utils/React_utils.framework/Headers\" \"${PODS_CONFIGURATION_BUILD_DIR}/React-featureflags/React_featureflags.framework/Headers\" \"${PODS_CONFIGURATION_BUILD_DIR}/React-debug/React_debug.framework/Headers\" \"${PODS_CONFIGURATION_BUILD_DIR}/React-ImageManager/React_ImageManager.framework/Headers\" \"${PODS_CONFIGURATION_BUILD_DIR}/React-rendererdebug/React_rendererdebug.framework/Headers\"")
         assert_equal(spec.pod_target_xcconfig["CLANG_CXX_LANGUAGE_STANDARD"], "c++20")
         assert_equal(spec.pod_target_xcconfig["OTHER_CPLUSPLUSFLAGS"], "$(inherited) -DRCT_NEW_ARCH_ENABLED=1 "+ folly_compiler_flags)

packages/react-native/scripts/cocoapods/new_architecture.rb

@@ -99,7 +99,7 @@ def self.install_modules_dependencies(spec, new_arch_enabled, folly_version = ge
                 }
         end
         header_search_paths_string = header_search_paths.join(" ")
-        spec.compiler_flags = compiler_flags.empty? ? folly_compiler_flags : "#{compiler_flags} #{compiler_flags}"
+        spec.compiler_flags = compiler_flags.empty? ? self.computeFlags(new_arch_enabled).strip! : "#{compiler_flags} #{self.computeFlags(new_arch_enabled)}"
         current_config["HEADER_SEARCH_PATHS"] = current_headers.empty? ?
             header_search_paths_string :
             "#{current_headers} #{header_search_paths_string}"