Remove current build before upgrade.

[orhtej2]

Problem

As per #26 upgrade to 2.6.2 fails due to, presumably, some stale files present.

Solution

• Remove build dir before unpacking the sources

PR Status

• [x] Code finished and ready to be reviewed/tested
• [x] The fix/enhancement were manually tested (if applicable)

Automatic tests

Automatic tests can be triggered on https://ci-apps-dev.yunohost.org/ after creating the PR, by commenting "!testme", "!gogogadgetoci" or "By the power of systemd, I invoke The Great App CI to test this Pull Request!". (N.B. : for this to work you need to be a member of the Yunohost-Apps organization)

[orhtej2]

!testme

[yunohost-bot]

:carousel_horse: