    'ndk-build' Overview

    I. Usage:
    ---------

    The Android NDK r4 introduced a new tiny shell script, named 'ndk-build',
    to simplify building machine code.

    The script is located at the top-level directory of the NDK, and shall
    be invoked from the command-line when in your application project
    directory, or any of its sub-directories. For example:

        cd $PROJECT
        $NDK/ndk-build

    Where $NDK points to your NDK installation path. You can also create an
    alias or add $NDK to your PATH to avoid typing it every time.

    II. Options:
    ------------

    All parameters to 'ndk-build' are passed directly to the underlying GNU Make
    command that runs the NDK build scripts. Notable uses include:

      ndk-build                  --> rebuild required machine code.
      ndk-build clean            --> clean all generated binaries.

      ndk-build NDK_DEBUG=1      --> generate debuggable native code.

      ndk-build V=1              --> launch build, displaying build commands.

      ndk-build -B               --> force a complete rebuild.

      ndk-build -B V=1           --> force a complete rebuild and display build
                                     commands.

      ndk-build NDK_LOG=1        --> display internal NDK log messages
                                     (used for debugging the NDK itself).

      ndk-build NDK_DEBUG=1      --> force a debuggable build (see below)
      ndk-build NDK_DEBUG=0      --> force a release build (see below)

      ndk-build NDK_APPLICATION_MK=<file>
        --> rebuild, using a specific Application.mk pointed to by
            the NDK_APPLICATION_MK command-line variable.

      ndk-build -C <project>     --> build the native code for the project
                                     path located at <project>. Useful if you
                                     don't want to 'cd' to it in your terminal.

    III. Debuggable versus Release builds:
    --------------------------------------

    In NDK r5, ndk-build has been modified to make it easier to switch between
    release and debug builds. This is done by using the NDK_DEBUG variable.
    For example:

      $NDK/ndk-build NDK_DEBUG=1  => forces the generation of debug binaries
      $NDK/ndk-build NDK_DEBUG=0  => forces the generation of release binaries

    If you don't specify NDK_DEBUG, ndk-build will keep its default behaviour,
    which is to inspect the AndroidManifest.xml, if any, and see if its
    <application> element has android:debuggable="true".

    IMPORTANT: If you use the build tools of SDK r8 (or higher), you
               won't need to touch your AndroidManifest.xml file at all!

               That's because if you build a debug package (e.g. with
               "ant debug" or the corresponding option of the ADT plugin),
               the tool will  automatically pick the native debug files
               generated with NDK_DEBUG=1.

    Also, as a convenience, the release and debug object files generated by the
    NDK are now stored in different directories (e.g. obj/local/<abi>/objs and
    obj/local/<abi>/objs-debug). This avoids having to recompile all your sources
    when you switch between these two modes (even when you only modified one or
    two source files).

    IV. Requirements:
    -----------------

    You need GNU Make 3.81 or later to use 'ndk-build' or the NDK in general.
    The build scripts will detect that you're using a non-compliant Make tool
    and will complain with an error message.

    If you have GNU Make 3.81 installed, but that it is not launched by the
    default 'make' command, define GNUMAKE in your environment to point to it
    before launching 'ndk-build'. For example:

        GNUMAKE=/usr/local/bin/gmake ndk-build

    Or to make the change more permanent:

        export GNUMAKE=/usr/local/bin/gmake
        ndk-build

    Adapt to your shell and GNU Make 3.81 installation location.

    V. Internals:
    -------------

    'ndk-build' itself is a tiny wrapper around GNU Make, its purpose is simply
    to invoke the right NDK build script, it is equivalent to;

        $GNUMAKE -f $NDK/build/core/build-local.mk [parameters]

    Where '$GNUMAKE' points to GNU Make 3.81 or later, and $NDK points to your
    NDK installation directory.

    Use this knowledge if you want to invoke the NDK build script from other
    shell scripts (or even your own Makefiles).