Rework androidenv package generation

androidenv did not previously write license files, which caused certain
gradle-based Android tools to fail. Restructure androidenv's list of
Android packages into a single repo.json file to prevent duplication
and enable us to extract the EULA texts, which we then hash with
builtins.hashString to produce the license files that Android gradle
tools look for.

Remove includeDocs and lldbVersions, as these have been removed
from the Android package repositories.

Improve documentation and examples.

pkgs/development/mobile/androidenv/generate.sh

@@ -1,36 +1,3 @@
-#!/usr/bin/env nix-shell
-#!nix-shell -i bash -p curl libxslt
+#!/bin/sh
 
-set -e
-
-die() {
-    echo "$1" >&2
-    exit 1
-}
-
-fetch() {
-    local url="https://dl.google.com/android/repository/$1"
-    echo "$url -> $2"
-    curl -s "$url" -o "$2" || die "Failed to fetch $url"
-}
-
-pushd "$(dirname "$0")" &>/dev/null || exit 1
-
-mkdir -p xml
-
-# Convert base packages
-fetch repository2-1.xml xml/repository2-1.xml
-xsltproc convertpackages.xsl xml/repository2-1.xml > generated/packages.nix
-
-# Convert system images
-for img in android android-tv android-wear android-wear-cn google_apis google_apis_playstore
-do
-    fetch sys-img/$img/sys-img2-1.xml xml/$img-sys-img2-1.xml
-    xsltproc --stringparam imageType $img convertsystemimages.xsl xml/$img-sys-img2-1.xml > generated/system-images-$img.nix
-done
-
-# Convert system addons
-fetch addon2-1.xml xml/addon2-1.xml
-xsltproc convertaddons.xsl xml/addon2-1.xml > generated/addons.nix
-
-popd &>/dev/null
+./fetchrepo.sh && ./mkrepo.sh