Build only arm64 when building PRs. All archs for nightlies and releases. (#38816)

Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/38816

To save resources, we should build only arm64 for PRs and commits to mains.
Our Android ABIs are really similar and we should just build the most popular. For nightlies/releases
instead we'll have to build all the archs.

Changelog:
[Internal] [Changed] - Build only arm64 when building PRs. All archs for nightlies and releases.

Reviewed By: cipolleschi

Differential Revision: D48112361

fbshipit-source-id: 69e172a4ea69f844b344a9fc6ac4ee0471b40c36

.circleci/config.yml

@@ -31,6 +31,8 @@ references:
     environment:
       - TERM: "dumb"
       - GRADLE_OPTS: '-Dorg.gradle.daemon=false'
+      # By default we only build ARM64 to save time/resources. For release/nightlies, we override this value to build all archs.
+      - ORG_GRADLE_PROJECT_reactNativeArchitectures: "arm64-v8a"
       # Repeated here, as the environment key in this executor will overwrite the one in defaults
       - PUBLIC_ANALYSISBOT_GITHUB_TOKEN_A: *github_analysisbot_token_a
       - PUBLIC_ANALYSISBOT_GITHUB_TOKEN_B: *github_analysisbot_token_b
@@ -1844,6 +1846,14 @@ jobs:
           command: |
             mkdir -p ~/.ssh
             echo '|1|If6MU203eXTaaWL678YEfWkVMrw=|kqLeIAyTy8pzpj8x8Ae4Fr8Mtlc= ssh-rsa AAAAB3NzaC1yc2EAAAABIwAAAQEAq2A7hRGmdnm9tUDbO9IDSwBK6TbQa+PXYPCPy6rbTrTtw7PHkccKrpp0yVhp5HdEIcKr6pLlVDBfOLX9QUsyCOV0wzfjIJNlGEYsdlLJizHhbn2mUjvSAHQqZETYP81eFzLQNnPHt4EVVUh7VfDESU84KezmD5QlWpXLmvU31/yMf+Se8xhHTvKSCZIFImWwoG6mbUoWf9nzpIoaSjB+weqqUUmpaaasXVal72J+UX2B+2RPW3RcT0eOzQgqlJL3RKrTJvdsjE3JEAvGq3lGHSZXy28G3skua2SmVi/w4yCE6gbODqnTWlg7+wC604ydGXA8VJiS5ap43JXiUFFAaQ==' >> ~/.ssh/known_hosts
+      - run:
+          name: Set the reactNativeArchitectures to build only required architectures
+          command: |
+            if [ "${release_type}" = "dry-run" ]; then
+              export ORG_GRADLE_PROJECT_reactNativeArchitectures="arm64-v8a"
+            else
+              export ORG_GRADLE_PROJECT_reactNativeArchitectures="armeabi-v7a,arm64-v8a,x86,x86_64"
+            fi
       - checkout
       - *attach_hermes_workspace
       - run: