readme: Improve Android docs and update GStreamer runtime deps (#31171)

The Android documentation was missing a few packages that needed to be
installed as well as some quotes to properly run the commands. In
addition, trim down the build setup and move the more complex contents
to the wiki.

Update the GStreamer runtime deps to reflect reality.

README.md

@@ -60,6 +60,29 @@ manually, try the [manual build setup][manual-build].
 
 See also [Windows Troubleshooting Tips][windows-tips].
 
+### Android
+
+- Ensure that the following environment variables are set:
+  - `ANDROID_SDK_ROOT`
+  - `ANDROID_NDK_ROOT`: `$ANDROID_SDK_ROOT/ndk/25.2.9519653/`
+ `ANDROID_SDK_ROOT` can be any directory (such as `~/android-sdk`).
+  All of the Android build dependencies will be installed there.
+- Install the latest version of the [Android command-line
+  tools](https://developer.android.com/studio#command-tools) to
+  `$ANDROID_SDK_ROOT/cmdline-tools/latest`.
+- Run the following command to install the necessary components and the path t
+  ```shell
+  sudo $ANDROID_SDK_ROOT/cmdline-tools/latest/bin/sdkmanager --install
+   "build-tools;33.0.2" \
+   "emulator" \
+   "ndk;25.2.9519653" \
+   "platform-tools" \
+   "platforms;android-33" \
+   "system-images;android-33;google_apis;x86_64"
+  ```
+For information about building and running the Android build, see
+the [Android documentation][android-docs].
+
 ### Cloning the Repo
 Your CARGO_HOME needs to point to (or be in) the same drive as your Servo repository (See [#28530](https://github.com/servo/servo/issues/28530)).
 ``` sh
@@ -108,6 +131,14 @@ Add the `--release` flag to create an optimized build:
 ./mach run --release tests/html/about-mozilla.html
 ```
 
+### Android build
+
+For an armv7 Android build run the following command.
+
+```shell
+./mach build --android
+```
+
 ### Checking for build errors, without building
 
 If you’re making changes to one crate that cause build errors in another crate,
@@ -122,49 +153,6 @@ It will run `cargo check`, which runs the analysis phase of the compiler
 This can be a lot faster than a full build,
 though of course it doesn’t produce a binary you can run.
 
-### Building for Android target
-
-Prerequisites:
-Servo's build system assumes that both the Android SDK & NDK are
-already installed and expects the paths to be specified via the
-environment variables `ANDROID_SDK_ROOT` and `ANDROID_NDK_ROOT`.
-
-Servo also expects the following components are installed via
-sdkmanager:
-
-For building:
-
-``` sh
-sdkmanager install platform-tools platforms;android-33
-```
-
-To run in emulator, also install the related components:
-
-``` sh
-sdkmanager install emulator system-images;android-33;google_apis;x86
-```
-
-Build commands:
-For ARM (`armv7-linux-androideabi`, most phones):
-
-``` sh
-./mach build --release --android
-./mach package --release --android
-```
-
-For x86 (typically for the emulator):
-
-```sh
-./mach build --release --target i686-linux-android
-./mach package --release --target i686-linux-android
-```
-
-Install the APK to the device or emulator:
-
-``` sh
-./mach install --release --android
-```
-
 ## Running
 
 Run Servo with the command:
@@ -199,8 +187,8 @@ Run Servo with the command:
 
 #### Linux
 
-* `GStreamer` >=1.16
-* `gst-plugins-bad` >=1.16
+* `GStreamer` >=1.18
+* `gst-plugins-bad` >=1.18
 * `libXcursor`
 * `libXrandr`
 * `libXi`
@@ -217,3 +205,4 @@ The generated documentation can be found on https://doc.servo.org/servo/index.ht
 
 [manual-build]: https://github.com/servo/servo/wiki/Building#manual-build-setup
 [windows-tips]: https://github.com/servo/servo/wiki/Building#troubleshooting-the-windows-build
+[android-docs]: https://github.com/servo/servo/wiki/Android