Merge bitcoin#17365: depends: update README.md with working Android t…

…argets and API levels

3fe1aba depends: move README.md Android instructions to a separate section (Igor Cota)
aa9b84a depends: update README.md with working Android targets and API levels (Igor Cota)

Pull request description:

  Per @Sjors comments in bitcoin#16110 (review)

ACKs for top commit:
  Sjors:
    ACK 3fe1aba

Tree-SHA512: 7a2e676070d51c7a4291b0d4b638f52321c08cc6ebe2bd2c02ba62f6cc3dd8a73227df4693c6ce9201863eb0bf26e0133805347b9016cb0f9a389a49cc9492aa

depends/README.md

@@ -30,17 +30,12 @@ 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.
-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:
-
-    ANDROID_SDK=/home/user/Android/Sdk ANDROID_NDK=/home/user/Android/Sdk/ndk-bundle make HOST=aarch64-linux-android ANDROID_API_LEVEL=28 ANDROID_TOOLCHAIN_BIN=/home/user/Android/Sdk/ndk-bundle/toolchains/llvm/prebuilt/linux-x86_64/bin
-
-
+The paths are automatically configured and no other options are needed unless targeting [Android](#Android).
 
 ### Install the required dependencies: Ubuntu & Debian
 
@@ -99,6 +94,19 @@ options will be passed to bitcoin's configure. In this case, `--disable-wallet`.
     download-win: run 'make download-win' to fetch all sources needed for win builds
     download-linux: run 'make download-linux' to fetch all sources needed for linux builds
 
+
+### 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:
+
+    ANDROID_SDK=/home/user/Android/Sdk ANDROID_NDK=/home/user/Android/Sdk/ndk-bundle make HOST=aarch64-linux-android ANDROID_API_LEVEL=28 ANDROID_TOOLCHAIN_BIN=/home/user/Android/Sdk/ndk-bundle/toolchains/llvm/prebuilt/linux-x86_64/bin
+
 ### Other documentation
 
 - [description.md](description.md): General description of the depends system