code: function doWhich () {
      // On Windows use msbuild provided by node-gyp configure
      if (win && config.variables.msbuild_path) {
        command = config.variables.msbuild_path
        log.verbose('using MSBuild:', command)
        doBuild()
        return
      }
      // First make sure we have the build command in the PATH
      which(command, function (err, execPath) {
        if (err) {
          if (win && /not found/.test(err.message)) {
            // On windows and no 'msbuild' found. Let's guess where it is
            findMsbuild()
          } else {
            // Some other error or 'make' not found on Unix, report that to the user
            callback(err)
          }
          return
        }
        log.verbose('`which` succeeded for `' + command + '`', execPath)
        doBuild()
      })
    }
docs: Uses node-which to locate the msbuild / make executable.