Build Hermes from source by default on iOS

Summary:
Remove BUILD_HERMES_SOURCE gate and default to building Hermes from source on iOS when Hermes is enabled.

Changelog:
[iOS][Changed] - When Hermes is enabled, the Hermes Engine will be built from source instead of using the pre-built `hermes-engine` CocoaPod.

Reviewed By: cortinico

Differential Revision: D34911987

fbshipit-source-id: 9d6d49498a23f6dae0b97c9f80c689b654db11bd

packages/rn-tester/Podfile.lock

@@ -94,7 +94,6 @@ PODS:
   - RCTRequired (1000.0.0)
   - RCTTypeSafety (1000.0.0):
     - FBLazyVector (= 1000.0.0)
-    - RCT-Folly (= 2021.06.28.00-v2)
     - RCTRequired (= 1000.0.0)
     - React-Core (= 1000.0.0)
   - React (1000.0.0):
@@ -908,7 +907,7 @@ SPEC CHECKSUMS:
   OpenSSL-Universal: ebc357f1e6bc71fa463ccb2fe676756aff50e88c
   RCT-Folly: 4d8508a426467c48885f1151029bc15fa5d7b3b8
   RCTRequired: 1c8808cf84569265784a6c33984bbb506ada8c6e
-  RCTTypeSafety: b9e639380265155a5bbdac4a72be1307f9360fc6
+  RCTTypeSafety: b6dcb5036a808864ee8cad66ca15f263c24661cc
   React: 8d809d414723bb5763093ddec7658066a21ccabc
   React-bridging: 1329cdc45834252447f5f4cb8bd19ec78ef0f06e
   React-callinvoker: 5f16202ad4e45f0607b1fae0f6955a8f7c87eef1

scripts/react_native_pods.rb

@@ -110,13 +110,8 @@ def use_react_native! (options={})
 
   if hermes_enabled
     pod 'React-hermes', :path => "#{prefix}/ReactCommon/hermes"
-
-    if ENV['BUILD_HERMES_SOURCE'] == '1'
-      hermes_source_path = downloadAndConfigureHermesSource(prefix)
-      pod 'hermes-engine', :path => "#{hermes_source_path}/hermes-engine.podspec"
-    else
-      pod 'hermes-engine', '~> 0.11.0'
-    end
+    hermes_source_path = downloadAndConfigureHermesSource(prefix)
+    pod 'hermes-engine', :path => "#{hermes_source_path}/hermes-engine.podspec"
     pod 'libevent', '~> 2.1.12'
   end
 
@@ -677,20 +672,6 @@ def downloadAndConfigureHermesSource(react_native_path)
   hermes_dir
 end
 
-def locatePathToHermesSource!(react_native_path)
-  return if ENV['BUILD_HERMES_SOURCE'] != '1'
-
-  hermes_source_path = "#{react_native_path}/sdks/hermes"
-
-  if !File.exist?(hermes_source_path)
-    Pod::UI.warn "[Hermes] Error: Hermes source code must be present at #{hermes_source_path} when BUILD_HERMES_SOURCE is enabled."
-    Pod::UI.warn '[Hermes] Verify that the release of React Native that you are using has the Hermes source code included.'
-    exit 1
-  end
-
-  hermes_source_path
-end
-
 # This provides a post_install workaround for build issues related Xcode 12.5 and Apple Silicon (M1) machines.
 # Call this in the app's main Podfile's post_install hook.
 # See https://github.com/facebook/react-native/issues/31480#issuecomment-902912841 for more context.