CI: build: fix parse toolchain step failing for git strict rules

CI: build: fix parse toolchain step failing for git strict rules

Commit 1cb8cdb ("ci: use new buildbot worker images with Debian 11")
introduced new Git version with strict rules for owner of the git
directory.

To handle this and not cause major change, just move the parsing before
the change of ownership of the openwrt directory permitting the correct
run of git fetch command with the same user that did the repository
checkout.

Fixes: 1cb8cdb ("ci: use new buildbot worker images with Debian 11")
Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
(cherry picked from commit 0063e71d66766818fba286efe2a0ed8746c265e5)