doc: add command options to README.md

Documents options accepted by node-gyp.
Continuation of nodejs#880.

README.md

@@ -44,11 +44,11 @@ You will also need to install:
  * On Windows:
  * Visual C++ Build Environment:
  * Option 1: Install [Visual C++ Build Tools](http://go.microsoft.com/fwlink/?LinkId=691126) using the **Default Install** option.
- 
+
  * Option 2: Install [Visual Studio 2015](https://www.visualstudio.com/products/visual-studio-community-vs) (or modify an existing installation) and select *Common Tools for Visual C++* during setup. This also works with the free Community and Express for Desktop editions.
- 
+
  > :bulb: [Windows Vista / 7 only] requires [.NET Framework 4.5.1](http://www.microsoft.com/en-us/download/details.aspx?id=40773)
- 
+
  * Install [Python 2.7](https://www.python.org/downloads/) (`v3.x.x` is not supported), and run `npm config set python python2.7` (or see below for further instructions on specifying the proper Python version and path.)
  * Launch cmd, `npm config set msvs_version 2015`
 
@@ -144,6 +144,7 @@ Commands
 
 | **Command** | **Description**
 |:--------------|:---------------------------------------------------------------
+| `help` | Shows the help dialog
 | `build` | Invokes `make`/`msbuild.exe` and builds the native addon
 | `clean` | Removes the `build` directory if it exists
 | `configure` | Generates project build files for the current platform
@@ -153,6 +154,34 @@ Commands
 | `remove` | Removes the node development header files for the given version
 
 
+Command Options
+--------
+
+`node-gyp` accepts the following command options:
+
+| **Command** | **Description**
+|:----------------------------------|:------------------------------------------
+| `-j n`, `--jobs n` | Run make in parallel
+| `--silly`, `--loglevel=silly` | Log all progress to console
+| `--verbose`, `--loglevel=verbose` | Log most progress to console
+| `--silent`, `--loglevel=silent` | Don't log anything to console
+| `--debug` | Make Debug build (default=Release)
+| `--release`, `--no-debug` | Make Release build
+| `--directory=$dir` | Run command in different directory
+| `--make=$make` | Override make command (e.g. gmake)
+| `--thin=$thin` | Enable thin static libraries
+| `--arch=$arch` | Set target architecture (e.g. ia32)
+| `--tarball=$path` | Get headers from a local tarball
+| `--ensure` | Don't reinstall headers if already present
+| `--dist-url=$url` | Download header tarball from custom URL
+| `--proxy=$url` | Set HTTP proxy for downloading header tarball
+| `--cafile=$cafile` | Override default CA chain (to download tarball)
+| `--nodedir=$path` | Set the path to the node binary
+| `--python=$path` | Set path to the python (2) binary
+| `--msys_version=$version` | Set Visual Studio version (win)
+| `--solution=$solution` | Set Visual Studio Solution version (win)
+
+
 License
 -------