bump targetSdk to 30 (again :p)

[pazos]

Binaries need to be bundled as shared libraries to avoid W^X on Android 10+

Is still possible to dlopen libraries from app home directory on Android 11, but that might change soon.

Symlink binaries stored in readable storage to the app home dir, where they're expected. Read symlinks from assets/module/map.txt

This works fine for binaries, but for shared libraries the minSdk needs to be bumped to API23. Since we're fine with targetSdk 30, as we were with targetSdk 28, there's no need to overcomplicate stuff for now.

At build time:

1. place shared libraries in libs/$(ANDROID_ABI)
2. place a symbolic map in assets/module/map.txt

At runtime map.txt is checked and symbolic links created.

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This change is 

[Frenzie]

If it works, then /shrug ;-)

[pazos]

If it works, then /shrug ;-)

It is a work in progress. It works fine for both sdcv and unversioned libraries. The only deal breaker is libluacompat52.so, which is found 3 times and only the last one is copied to platform/android/luajit-launcher/libs

My idea is to fix koreader/koreader-base#1237 first (deversioning but renaming as needed), put everything as jniLibs and make symbolic links that match other platforms at runtime using android.bootstrap()

This superseedes #175 and should fix #16

[pazos]

@Frenzie @NiLuJe: this is ready to review. Works fine on top of current master.

Mainly we attempt to extract all assets in "module" in a single step.

for each asset:

• if it is an 7z file extract it on filesDir
• if it is a file called "module/map.txt" parse it and link nativeLibsDir to filesDir
• if it is a file other than "module/version.txt" copy it on filesDir.

Other minor changes:

• we read the version from a text file
• the dots "dialog" is started each time we attempt to bootstrap assets and last the entire asset extraction, including linking and copying raw assets.

[Frenzie]

No real comments while reading, but I haven't yet tested it.

[pazos]

Updated to support executing sdcv with targetSdk 30. Shared libraries are untouched as there's no way to get them outside filesDir that works across supported android versions.

Another related topic is the translation of https://github.com/koreader/android-luajit-launcher/blob/master/app/src/main/res/values/strings.xml. Since we have different projects hosted on weblate I think we can afford one extra project :)

[pazos]

Updated to support executing sdcv with targetSdk 30. Shared libraries are untouched as there's no way to get them outside filesDir that works across supported android versions.

Updated on top of master, which a few other fixes for recent-ish changes. Ready to be reviewed (and hopefully merged)

[Frenzie]

No comment. I trust you on the symlink stuff. ;-)