Support tilde expansion in build_dir (and maybe others)

[pakal]

As of the current master, build_dir is joined with root directory (which is thus ignored if build_dir is an absolute path), and realpath() is applied on it.

It'd be handy to perform tilde expansion on all builder spec paths, since for example one needs to use a Linux VM (on Windows) to sue buildozer, and the .buildozer/ dir should not be in the shared folder where the app code is stored (because of symlinks and other badly supported features of shared folders).

Hence using the VM user's HOME to store build artifacts would be handy, without hardcoding it into the GIT-shared buildozer.spec file.

PS: thanks for the very handy build toolchain, I'm having lots of fun with it and Kivy

[AndreMiras]

Thanks for the report @pakal
I do use the tild for some of these settings, but I have never tried with build_dir.
Would you mind making a pull request to fix it?

[pakal]

I added this expansion to every realpath() operation, is it OK ?

However i'm not sure how it could be tested, that's the kind of tiny details which are not covered by the test suite :?

[AndreMiras]

Thanks for the PR.
Indeed these details are not yet covered given we have a very low code coverage currently. You could try testing a couple of them maybe