Add comment about how the cbindgen-vendor.tar.bz2 got created

We should add a comment about how the cbindgen vendor .bz2 file came into place (I forgot to do that in legacy/trac#30490 (moved)).

added GeorgKoppen201911 in Legacy / Trac TorBrowserTeam201911 in Legacy / Trac actualpoints::0.1 in Legacy / Trac component::applications/tor browser in Legacy / Trac owner::tbb-team in Legacy / Trac points::0.1 in Legacy / Trac priority::medium in Legacy / Trac resolution::fixed in Legacy / Trac severity::normal in Legacy / Trac status::closed in Legacy / Trac tbb-rbm in Legacy / Trac type::defect in Legacy / Trac labels

bug_32509 (https://gitweb.torproject.org/user/gk/tor-browser-build.git/commit/?h=bug_32509&id=ead3b276006b68a7eecac3f29f09c1d4df76350c) in my public tor-browser-build repo has a patch for review.

Trac:
Points: N/A to 0.1
Keywords: N/A deleted, TorBrowserTeam201911, GeorgKoppen201911 added
Status: new to needs_review

This looks good to me, thanks. I merged it to master as commit ead3b276006b68a7eecac3f29f09c1d4df76350c.

Trac:
Status: needs_review to closed
Resolution: N/A to fixed

Trac:
Actualpoints: N/A to 0.1

closed

changed time estimate to 48m

added 48m of time spent

moved from legacy/trac#32509 (moved)

added Bug label and removed 1 deleted label

removed 1 deleted label