win,build: add arbitrary and binlog options

This change adds a 'msbuild_arg' option to vcbuild.bat that can be used
to pass arbitrary flags to MSBuild.

It also adds a 'binlog' flag as a shortcut 'msbuild_arg' option to
enable binary logging to `%config%\node.binlog`. This is especially
convenient when debugging changes to the build system.

In the process of developing this change, the idea of adding 'setlocal'
to the beginning of the script was rejected since other scripts in this
repo rely on the exported environment variables. This change adds a
note describing this.

PR-URL: https://github.com/nodejs/node/pull/25994


Reviewed-By: João Reis <reis@janeasystems.com>