@ivogabe any ideas what went wrong with the latest?

I thought that it only contained changes related to sourcemaps, but I'll take a look at it.

I think that the old behaviour was wrong and the current behaviour is correct. When a tsconfig file is placed in a subdirectory, gulp-typescript would emit incorrect paths, see ivogabe/gulp-typescript#461. Though this old behaviour seemed to work here.

Here's what happens:
src/compiler/tsconfig.json sets "outFile": "../../built/local/tsc.js". In the gulpfile, localCompilerProject.src() sets the base path of the source files to root/src/compiler. The generated file should then have root/src/compiler as base path too, and ../../built/local/tsc.js (value of outFile) as relative path. gulp.dest(".") then causes that this file is written as ../../built/local/tsc.js (thus, outside of the project directory).

Previously, the base path would be wrongly set to "" (yes, an empty string), which caused that the file would we written as built/local/tsc.js.

This can be fixed by using gulp.dest("src/compiler") (the location of the tsconfig file, such that the outFile is evaluated relative to this location), setting outFile: "built/local/tsc.js" (this path is relative to project root, so gulp.dest(".") works fine), or setting outFile: "tsc.js" and gulp.dest("built/local").