As I mentioned in my comment, I had a very similar problem. After installing node.js for purpose of using gulp I could not do a successful build. I would get the following error:
C:\Visual Studio
Projects\MyProject\packages\RazorGenerator.MsBuild.2.2.6\build\RazorGenerator.MsBuild.targets(21,9):
error : Illegal characters in path.
After searching around I guessed that the problem had to do with the node.js utilizing "illegally" long path names. For some background go here: https://github.com/joyent/node/issues/6960
My solution was to install the Flatten Packages tool: https://visualstudiogallery.msdn.microsoft.com/cd0b1938-4513-4e57-b9b7-c674b4a20e79?SRC=VSIDE
I ran flatten packages on the "node_modules" folder, tried to build (failed but with a different error), restarted Visual Studio, and everything now seems to build ok. Hope this helps.
UPDATE
One thing to keep in mind is that, by design, Flatten Packages will move files up in the directory structure. As a consequence, however, Visual Studio will still look for some of the folder/files in the OLD location; VS will shows the [!] symbol to show that the file was there but no longer is. These old file references can gum up the build, so you need to simply delete these old file references/directories.