[android] Update internal documentation on CoreCLR on Android experimental support

[ivanpovazan]

Description

This pull request updates the internal documentation with instructions for:

• Building CoreCLR for Android
• Building and running an Android sample application on CoreCLR
• Debugging the sample application and the runtime

This is intended for developers working on CoreCLR's support for Android.

NOTE: As the support is experimental, the documentation covers only currently supported scenarios, and will be updated in the future as we expand our support.

---

Fixes #111955

[ivanpovazan]

After discussion with @janvorli, we agreed to remove the outdated Linux documentation and to refer to MacOS one.

[akoeplinger]

do you really need to symlink or would it be enough to set xharness ADB_EXE_PATH to /mnt/<path-to-adb-on-host> ?

[ivanpovazan]

@elinor-fung ^

[elinor-fung]

I had to symlink it somewhere. It didn't necessarily need to be the path from the Android SDK in WSL2, but I found that convenient for just using adb from the command line in WSL.

When I directly set ADB_EXE_PATH=/mnt/<path-to-adb-on-host>, running with xharness would fail with:

Exit code: 1
Std out:
Performing Streamed Install
        
Std err:
adb: failed to stat /home/elinor/runtime/artifacts/bin/AndroidSampleApp/x64/Release/android-x64/Bundle//bin/HelloAndroid.apk: No such file or directory

I admittedly didn't really spend time looking into why.

Directly running /mnt/<path-to-adb-on-host> install <path-to-apk-in-wsl> from my WSL terminal works fine, so I guess it may be something with how it gets launched with xharness?

[ivanpovazan]

@kotlarmilos could you include a note about the problem you were having with Cannot invoke "String.length()" because "<parameter1>" is null , and how you resolved it?

[ivanpovazan]

/ba-g wasm jobs not affected