Cabal-3.4 release candidate 1

[Oleg Grenrus]

Dear all,

Last week I tagged Cabal-3.4 release candidate. After fixing few
immediately obvious issues with cabal-install, I have successfully used
it for a week.

This week I have been working on improving scripts for bootstrapping and
release packaging, and as intermediate result there are

- x86_64-darwin-sierra
- x86_64-ubuntu-14.04
- x86_64-alpine-3.11.6
- amd64-freebsd-12.1-RELEASE
- aarch64-ubuntu-18.04

bootstrapped builds at

https://oleg.fi/cabal-install-3.4.0.0-rc1-bootstrapped/

The ubuntu-14.04 build works on later ubuntu, debian, and centos which I
tried (in docker). Note, alpine build is not static, i.e. it dynamically
links against musl.

Please try these out, especially try to build cabal-install (from 3.4)
branch, and use it, so we can fix most of regressions since 3.2.
I'm specially interested whether the darwin/macos build works on newer
macos versions.

The release notes for Cabal-3.4 and cabal-install-3.4 are available at
https://github.com/haskell/cabal/tree/master/release-notes

- Oleg