gulpfile.js

...

var legacyScriptsArr = [
  './path/to/legacy-script1.js',
  './path/to/legacy-script2.js',
  './path/to/legacy-script3.js',
  './path/to/legacy-script4.js',
  './path/to/legacy-script5.js',
];

gulp.task('testCompile1', function(done){
  return browserify(browserifyEntries)
  .transform(hbsfy)
  .transform(uglifyify)
  .bundle()
  .pipe(source('browserified.js'))
  .pipe(gulp.src(legacyScriptsArr))
  .pipe(tap(0))
  .pipe(gulp.dest('./assets/compiled/'))
  .on('end', done);
});

gulp.task('testCompile2', function(){
  return gulp.src(legacyScriptsArr)
  .pipe(tap(0))
  .pipe(gulp.dest('./assets/compiled/'));
});