Move GN_EXTRA_ARGS to gn gen step

.github/workflows/mac-build.yml

@@ -243,16 +243,8 @@ jobs:
       run: |
         (cd src/electron && git checkout .) && node src/electron/script/generate-deps-hash.js && cat src/electron/.depshash-target
         echo "DEPSHASH=$(shasum src/electron/.depshash | cut -f1 -d' ')" >> $GITHUB_ENV
-    - name: Setup Environment Variables
-      run: |
-        echo "CHROMIUM_BUILDTOOLS_PATH=$(pwd)/src/buildtools" >> $GITHUB_ENV
-
-        if [[ ${{ matrix.build-type }} == "darwin" ]]; then
-          echo 'GN_EXTRA_ARGS=target_cpu = "arm64"' >> $GITHUB_ENV
-        else
-          echo 'GN_EXTRA_ARGS=is_mas_build = true target_cpu = "arm64"' >> $GITHUB_ENV
-          echo "MAS_BUILD=true" >> $GITHUB_ENV
-        fi
+    - name: Add CHROMIUM_BUILDTOOLS_PATH to env
+      run: echo "CHROMIUM_BUILDTOOLS_PATH=$(pwd)/src/buildtools" >> $GITHUB_ENV
     - name: Fix Sync
       # This step is required to correct for differences between "gclient sync"
       # on Linux and the expected state on macOS. This requires:
@@ -318,6 +310,15 @@ jobs:
         echo 'RBE_experimental_credentials_helper_args=print' >> $GITHUB_ENV
     - name: Default GN gen
       run: |
+        if [[ "${{ matrix.build-type }}" == "darwin" ]]; then
+          GN_EXTRA_ARGS='target_cpu = "arm64"'
+        else
+          GN_EXTRA_ARGS='is_mas_build = true target_cpu = "arm64"'
+          echo "MAS_BUILD=true" >> $GITHUB_ENV
+        fi
+
+        echo "GN_EXTRA_ARGS is ${GN_EXTRA_ARGS}!"
+
         cd src/electron
         # TODO(codebytere): remove this once we figure out why .git/packed-refs is initially missing
         git pack-refs