Right now, running `tt_fpga.py --project-dir example/<projectname>
harden` will fail if previously, `tt_fpga.py harden` was ran against a
project in the root folder. This is because the `_tt_fpga_top.v` file is
always read from `src/_tt_fpga_top.v`, even though it's generated in the
proper --project-dir location.
Similar problem affects the `configure` command, where it looks for the
bitstream in `build/<name>.bin` relative to the current dir even with
`--project-dir` set.
Commit prepends the source_dir from `--project-dir` in the appropriate
places such that it's used for both harden and configure.
Tested by observing that running the following commands in sequence now
succeeds against one of my projects:
- tt_fpga.py harden
- tt_fpga.py --project-dir examples/tt_um_vga_example_gamepad harden
- tt_fpga.py --project-dir examples/tt_um_vga_example_gamepad configure
--upload --port /dev/ttyACM0
