using multiple baseUrl's when building with require.js

I have a project with a structure that looks similar to this:

/path/to/project
    /apps
        /app1
            /js
                /modules
                    /bar.js
                    /etc..
                /app1.js
                /app1.build.js
        /foo
            /app2
                /js
                    /modules
                        /cad.js
                        /etc..
                    /app2.js
                    /app2.build.js
    /static
        /js
            /libraries
                /jQuery
                /etc...
            /common-config.js
            /common-build-config.js

common-config.js defines a set of paths for loading libraries that is relative to the web-root of the project that both app1 and app2 can use. The goal of common-build-config.js is to provide similar functionality for the build process. The problem I am encountering is that I cannot use fully-qualified paths in common-build-config.js, as path/to/project is dependent on a number of factors (environment, project branch, server, etc), and relative paths fail because the relative paths from app1 and app2 to common-build-config.js are different. Module loading in app1 and app2 assumes that the base directory is the app directory, so I cannot change the baseUrl parameter in the app[x].build.js files without manually specifying paths for a ton of modules.

Is there a way I can specify baseUrl in common-build-config.js such that it will not affect the path loading in either of the main.build.js files? Alternatively, is there a way to use variables when defining paths in the build config (like getting the value of Node's __dirName variable)? Or is there another approach that can end-route this problem?

Example files:

[/path/to/project/static/common-config.js]

requirejs.config({
    paths: {
        jquery: '/static/js/libraries/jquery/jquery',
        underscore: '/static/js/libraries/underscore/underscore',
        backbone: '/static/js/libraries/backbone/backbone'
    }
});

[/path/to/project/apps/app1/js/app1.js]

require(['/static/js/common-config.js'], function () {
    require([
        // Load common modules
        'jquery',
        'underscore',
        'backbone',
        // Load local modules
        'bar'
    ], function ($, _, backbone, bar) {
        // do stuff
    });
});

[/path/to/project/apps/app1/js/app1.build.js]

({
    name: 'app1',
    out: './app1.min.js',
    optimize: 'uglify',
    mainConfigFile: '../../../../static/js/common-build-config.js',
    findNestedDependencies: true
})

[/path/to/project/static/common-build-config.js]

It would be nice if I could do something like this without affecting the paths in app1.build.js:

requirejs.config({
    baseUrl: './',
    paths: {
        jquery: 'libraries/jquery/jquery',
        underscore: 'libraries/underscore/underscore',
        backbone: 'libraries/backbone/backbone'
    }
});

or something like this without getting an error like __dirName is not defined:

requirejs.config({
    paths: {
        jquery: __dirName + 'libraries/jquery/jquery',
        underscore: __dirName + 'libraries/underscore/underscore',
        backbone: __dirName + 'libraries/backbone/backbone'
    }
});

In case it's relevant, I build the min files from the project root with the commands:

node "static/js/libraries/require/r.js" -o "apps/app1/js/app1.build.js"
node "static/js/libraries/require/r.js" -o "apps/foo/app2/js/app2.build.js"