depends: update README.md with working Android targets and API levels

Author: icota

depends/README.md

@@ -30,11 +30,17 @@ Common `host-platform-triplets` for cross compilation are:
 - `aarch64-linux-gnu` for Linux ARM 64 bit
 - `riscv32-linux-gnu` for Linux RISC-V 32 bit
 - `riscv64-linux-gnu` for Linux RISC-V 64 bit
+- `armv7a-linux-android` for Android ARM 32 bit
 - `aarch64-linux-android` for Android ARM 64 bit
+- `i686-linux-android` for Android x86 32 bit
+- `x86_64-linux-android` for Android x86 64 bit
 
 The paths are automatically configured and no other options are needed unless targeting Android.
 Before proceeding with an Android build one needs to get the [Android SDK](https://developer.android.com/studio) and use the "SDK Manager" tool to download the NDK and one or more "Platform packages" (these are Android versions and have a corresponding API level).
 In order to build `ANDROID_API_LEVEL` (API level corresponding to the Android version targeted, e.g. Android 9.0 Pie is 28 and its "Platform package" needs to be available) and `ANDROID_TOOLCHAIN_BIN` (path to toolchain binaries depending on the platform the build is being performed on) need to be set.
+
+API levels from 24 to 29 have been tested to work.
+
 If the build includes Qt, environment variables `ANDROID_SDK` and `ANDROID_NDK` need to be set as well but can otherwise be omitted.
 This is an example command for a default build with no disabled dependencies: