MODULES: lib, main

STEP 0:
    libs: lib, main
    dirty js modules: main, lib
    dirty js files:   lib/foo/f1, main/m, main/m.export, main
STEP 1:
    libs: lib, main
    dirty js modules: lib
    dirty js files:   lib/foo/f1
STEP 2:
    libs: lib, main
    dirty js modules: lib
    dirty js files:   lib/foo/f1, lib/foo/f1.export, lib
STEP 3:
    libs: lib, main
    dirty js modules: lib, main
    dirty js files:   lib/foo/f1, lib/foo/f1.export, main/m
STEP 4:
    libs: lib, main
    dirty js modules: lib
    dirty js files:   lib/foo/f1, lib/foo/f2, lib/foo/f1.export