options.mime strings don't expand grunt-config values

[cayleyh]

Working with a Gruntfile with different environments configured via grunt-config. Setting a value in options.mime based on the build destination like this:

aws_s3: {
   options: {
      mime: { '<%= grunt.config.get("BUILD_DIR") %>/file', 'application/json' }
   }
   ...
}

Doesn't work because the value for BUILD_DIR never gets substituted correctly. The mime object that is checked contains the literal string '<%= grunt.config.get("BUILD_DIR") %>/file' for the file path.

Very likely this is an issue with with Grunt or grunt-config directly, but thought I would raise it as I just spent 15 mins figuring out what was wrong :)