Expand the set up section of the README (#220)

First, CMake and Ninja are required, so tell people to install them.

Second, the way that Gradle works requires a few specific call-outs in our setup instructions:

1. Echo Java 17 requiement. Gradle is used to build the Android part of GFXR. Each version of Gradle has a maximum supported version of Java; see: https://docs.gradle.org/current/userguide/compatibility.html. GFXR uses Gradle 8.1 which has a max supported version of Java 19 (to invoke Gradle itself). While technically 18 and 19 are supported, Debian does not provide those versions through the package manager.
2. While Gradle will automatically download the SDK and NDK that it needs for a project, it will only do so if you have accepted the licenses. The easiest way to do this is to install Android Studio get an SDK through the setup process. After accepting the licenses, Gradle will be happy to take care of the rest. Also, Android Studio is essentially the only way to attach a debugger to Android apps.

Author: footballhead

README.md

@@ -11,6 +11,8 @@ git submodule update --init --recursive
 
 ### Prerequisite
 
+ - CMake
+ - Ninja
  - The QT framework, can be installed from [QT online installer](https://download.qt.io/archive/online_installers/4.6/). We are currently using QT 5.15.2. Note that to install QT 5.15.2 from the online installer, you have to enable (turn on) the `archived` versions and then click on `filter`.
  - gRPC [dependencies](https://github.com/grpc/grpc/blob/master/BUILDING.md#pre-requisites)
  - Android NDK (currently we are using 25.2.9519653). Set the `ANDROID_NDK_HOME` environment variable.
@@ -22,7 +24,12 @@ git submodule update --init --recursive
   ```
     pip install Mako
   ```
- - gfxreconstruct [dependencies](https://github.com/LunarG/gfxreconstruct/blob/dev/BUILD.md#android-development-requirements), if targetting Android
+ - gfxreconstruct [dependencies](https://github.com/LunarG/gfxreconstruct/blob/dev/BUILD.md#android-development-requirements), if targetting Android. Specifically:
+   - Android Studio. Make sure to install an SDK and accept the licenses.
+   - Java 17. Because it uses an older version of Gradle. Set the `JAVA_HOME` environment variable before building:
+     ```
+     export JAVA_HOME=/usr/lib/jvm/java-17-openjdk-amd64
+     ```
 
 ### Building Dive host tool on Linux
 ```