Copy component.json to a work folder, parse and then nuke the work folder. I did this because `grunt.file.expand` was too slow on my project structure, especially with all the node_modules folders present under multiple sub-projects.

GruntFile.js

module.exports = function (grunt) {
    'use strict';
    
    require('load-grunt-tasks')(grunt);
    grunt.renameTask('clean', 'nuke');

    grunt.initConfig({
        nuke: {
            work: ['work']
        },
        shell: {
            warmup: {
                options: {
                    stdout: true
                },
                command: 'for config in `find . -name component.json -maxdepth 2 -not -path \'./bootstrap/*\' -not -path \'./work/*\'`; do (parent=`dirname $config` && mkdir -p work/$parent && cp $config work/$parent/); done'
            }
        }
    });
    
    grunt.registerTask('cook', 'Generate the moduleMap', function () {
        var map = {},
            features = grunt.file.expand({
                filter: 'isFile'
            }, [
                './work/**/component.json'
            ]);

        features.forEach(function (feature) {
            var config = require(feature);
            map[config.name] = {
                version: config.version
            };
        });

        grunt.file.write('bootstrap/lib/moduleMap.js', 'module.exports=' + JSON.stringify(map));
    });

    grunt.registerTask('warmup', [
        'shell:warmup',
        'cook',
        'nuke'
    ]);
};

output

$ grunt warmup
Running "shell:warmup" (shell) task

Running "cook" task

Running "nuke:work" (nuke) task
Cleaning work...OK

Done, without errors.

Elapsed time
loading tasks  156ms
shell:warmup   170ms
nuke:work      29ms
Total          355ms