Android build system usage:

m [-j] [<targets>] [<variable>=<value>...]


Ways to specify what to build:
  The common way to specify what to build is to set that information in the
  environment via:

    # Set up the shell environment.
    source build/envsetup.sh # Run "hmm" after sourcing for more info
    # Select the device and variant to target. If no argument is given, it
    # will list choices and prompt.
    lunch [<product>-<variant>] # Selects the device and variant to target.
    # Invoke the configured build.
    m [<options>] [<targets>] [<variable>=<value>...]

      <product> is the device that the created image is intended to be run on.
        This is saved in the shell environment as $TARGET_PRODUCT by `lunch`.
      <variant> is one of "user", "userdebug", or "eng", and controls the
        amount of debugging to be added into the generated image.
        This gets saved in the shell environment as $TARGET_BUILD_VARIANT by
          `lunch`.

    Each of <options>, <targets>, and <variable>=<value> is optional.
      If no targets are specified, the build system will build the images
      for the configured product and variant.

  A target may be a file path. For example, out/host/linux-x86/bin/adb .
    Note that when giving a relative file path as a target, that path is
    interpreted relative to the root of the source tree (rather than relative
    to the current working directory).

  A target may also be any other target defined within a Makefile. Run
    `m help` to view the names of some common targets.

  To view the modules and targets defined in a particular directory, look for:
    files named *.mk (most commonly Android.mk)
      these files are defined in Make syntax
    files named Android.bp
      these files are defined in Blueprint syntax

  During a build, a few log files are generated in ${OUT} (or ${DIST_DIR}/logs
    for dist builds):

    verbose.log.gz
      every command run, along with its outputs. This is similar to the
      previous `m showcommands` option.
    error.log
      list of actions that failed during the build, and their outputs.
    soong.log
      verbose debug information from soong_ui

  For now, the full (extremely large) compiled list of targets can be found
    (after running the build once), split among these two files:

    ${OUT}/build-<product>*.ninja
    ${OUT}/soong/build.ninja

    If you find yourself interacting with these files, you are encouraged to
    provide a more convenient tool for browsing targets, and to mention the
    tool here.

Targets that adjust an existing build:
  dist                      Copy into ${DIST_DIR} the portion of the build
                            that must be distributed

Flags
  -j <N>                    Run <N> processes at once
  -j                        Autodetect the number of processes to run at once,
                            and run that many

Variables
  Variables can either be set in the surrounding shell environment or can be
    passed as command-line arguments. For example:
      export I_AM_A_SHELL_VAR=1
      I_AM_ANOTHER_SHELL_VAR=2 m droid I_AM_A_MAKE_VAR=3
  Here are some common variables and their meanings:
    TARGET_PRODUCT          The <product> to build # as described above
    TARGET_BUILD_VARIANT    The <variant> to build # as described above
    DIST_DIR                The directory in which to place the distribution
                            artifacts.
    OUT_DIR                 The directory in which to place non-distribution
                            artifacts.

  There is not yet known a convenient method by which to discover the full
  list of supported variables. Please mention it here when there is.