Issue 1414 - Document how to build libadblockplus for Android

README.md

Index: README.md
===================================================================
--- a/README.md
+++ b/README.md
@@ -10,16 +10,31 @@
 retrieved and updated during the build process, but you can also manually update
 them by running the following:
 
     ./ensure_dependencies.py
 
 Building
 --------
 
+### Supported compilers
+
+You need a C++11 compatible compiler to build libadblockplus.
+
+The compilation was tested with the following compilers:
+* g++ 4.8
+* Microsoft Visual Studio 2010, 2012
+* clang 3.4 for Android (from android-ndk-r9, android-ndk-r10c)
+* clang 3.6 for OS X
+* To compile for Android on linux one need to install g++-multilib
+
+You can download *android-ndk-r10c* for [Win 32](http://dl.google.com/android/ndk/android-ndk-r10c-windows-x86.exe), [Win 64](http://dl.google.com/android/ndk/android-ndk-r10c-windows-x86_64.exe), [OSX](http://dl.google.com/android/ndk/android-ndk-r10c-darwin-x86_64.bin), [Linux 32](http://dl.google.com/android/ndk/android-ndk-r10c-linux-x86.bin), [Linux 64](http://dl.google.com/android/ndk/android-ndk-r10c-linux-x86_64.bin).
+
+If you have a compilation issue with another compiler please [create an issue](https://issues.adblockplus.org/).
+
 ### Unix
 
 All you need is Python 2.7 and Make:
 
     make
 
 The default target architecture is x64. On a 32 bit system, run:
 
@@ -46,27 +61,27 @@
 `build\ia32\libadblockplus.sln` (solution for the 32 bit build) and
 `build\x64\libadblockplus.sln` (solution for the 64 bit build). Unfortunately,
 V8 doesn't support creating both from the same project files.
 * Open `build\ia32\libadblockplus.sln` or `build\x64\libadblockplus.sln` in
 Visual Studio and build the solution there. Alternatively you can use the
 `msbuild` command line tool, e.g. run `msbuild /m build\ia32\libadblockplus.sln`
 from the Visual Studio Developer Command Prompt to create a 32 bit debug build.
 
-### Supported compilers
+### Building for Android
 
-You need a C++11 compatible compiler to build libadblockplus.
+First set ANDROID_NDK_ROOT environment variable to your Android NDK directory.
 
-The compilation was tested with the following compilers:
-* g++ 4.8
-* Microsoft Visual Studio 2010, 2012
-* clang 3.4 for Android (from android-ndk-r9)
-* clang 3.6 for OS X
+To build for *x86* arch run:
 
-If you have a question about another compiler please [create an issue](https://issues.adblockplus.org/).
+    make android_x86
+
+To build for *arm* arch run:
+
+    make android_arm
 
 Usage
 -----
 
 You can use libadblockplus to build an ad blocker. Or, strictly speaking, a web
 content filter. Just like Adblock Plus, it can detect resources that should be
 blocked based on their URL and context information, and generate CSS selectors
 to hide DOM elements.