E3-1731: Don't install the makefile at the next level

The original e3 build installed the module.Makefile in the module
source directory, and then runs (essentially)
```
$ make -C module -f module.Makefile ARGS
```
However, there is no real need for it to copy it there instead of
simply using that makefile from the parent directory. This simplifies
a bit of the junk that gets added around during the build process.