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+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.
+
+  An alternative to setting $TARGET_PRODUCT and $TARGET_BUILD_VARIANT,
+  which you may see in build servers, is to execute:
+
+    make PRODUCT-<product>-<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
+
+  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:
+  showcommands              Display the individual commands run to implement
+                            the 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 make 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.
+