fix(cli): skip checks ndk when NDK_HOME set

[mslxl]

In the original code, the way to ensure NDK installation is to check whether the ndk folder exists under the $ANDROID_HOME directory. If it exists, the NDK_HOME environment variable is set; otherwise, the NDK will be installed. This approach overrides any user-set NDK_HOME variable. However, on some systems (like NixOS), the NDK installed via package managers may not be located in the $ANDROID_HOME/ndk directory but elsewhere. Ignoring the NDK_HOME variable would render such system-installed NDKs unusable.

This PR bypasses the NDK check when NDK_HOME has already been set.

[github-actions]

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