Rebuild rust against libgit2 0.28.1
Cargo fails to install after libgit2 has been updated to 0.28.1:
alpine-linux:~# apk add cargo
ERROR: unsatisfiable constraints:
so:libgit2.so.27 (missing):
required by: cargo-1.31.1-r1[so:libgit2.so.27]
(from redmine: issue id 10308, created on 2019-04-21, closed on 2019-04-23)