MODULES: lib1, lib2, main

STEP 0:
    libs: lib1, lib2, main
    dirty js modules: lib1, lib2, main
    dirty js files:   lib2/l2, lib1/f2, main/m.export, lib1/f1, main, main/m
STEP 1:
    libs: lib1, lib2, main
    dirty js modules: lib1
    dirty js files:   lib1/f1
