<key>CFBundleURLTypes</key>
<array>
<dict>
<key>CFBundleTypeRole</key>
<string>Editor</string>
<key>CFBundleURLSchemes</key>
<array>
<string>$(GOOGLE_SERVICES_REVERSE_CLIENT_ID)</string>
</array>
</dict>
</array>
Targets > Runner > Build Settings > Search “user” > User-Defined > GOOGLE_SERVICES_REVERSE_CLIENT_ID
設定した図
それぞれの環境のGoogleService-Info.plistから