Pinning NDK and use --active-arch-only on Android

[kraenhansen]

What, How & Why?

Fixed pinning of the NDK used to build our prebuilt binaries for Android. Our previous version, Realm JS v10.21.0 was compiled with NDK 25.1.8937393, which could result in unpredictable crashes, since this needs to match the one being used by React Native.

This closes potential crashes of 10.21.0 and the crashing integration tests on v11.

☑️ ToDos

• 📝 Changelog entry
• 📝 Compatibility label is updated or copied from previous entry
• 🚦 Tests
• 🔀 Executed flexible sync tests locally if modifying flexible sync
• 📦 Updated internal package version in consuming package.jsons (if updating internal packages)
• 📱 Check the React Native/other sample apps work if necessary
• 📝 Public documentation PR created or is not necessary
• 💥 Breaking label has been applied or is not necessary

[takameyer]

LGTM. I remember trying the --active-arch-only flag, but this did not seem to make much of a difference in build times.