ANN: stack-1.9 release candidate

[Emanuel Borsboom]

This is the first release candidate for stack-1.9.

Binaries for supported platforms are available here:
https://github.com/commercialhaskell/stack/releases/tag/v1.9.0.1

## Changes since v1.7.1

Release notes:

* Statically linked Linux bindists are back again, thanks to
[@nh2](https://github.com/nh2).
**Please try the `stack-1.9.0.1-linux-x86_64-static.tar.gz`
distribution if using Linux**, since it will be the default installed
version once v1.9.1 is released.
* We will be deleting the Ubuntu, Debian, CentOS, Fedora, and Arch
package repos from `download.fpcomplete.com` soon. These have been
deprecated for over a year and have not received new releases, but
were left in place for compatibility with older scripts.

Major changes:

* `GHCJS` support is being downgraded to 'experimental'. A warning
notifying the user of the experimental status of `GHCJS` will be
displayed.

Behavior changes:

* `ghc-options` from `stack.yaml` are now appended to `ghc-options` from
`config.yaml`, whereas before they would be replaced.
* `stack build` will now announce when sublibraries of a package are being
build, in the same way executables, tests, benchmarks and libraries are
announced
* `stack sdist` will now announce the destination of the generated tarball,
regardless of whether or not it passed the sanity checks
* The `--upgrade-cabal` option to `stack setup` has been
deprecated. This feature no longer works with GHC 8.2 and
later. Furthermore, the reason for this flag originally being
implemented was drastically lessened once Stack started using the
snapshot's `Cabal` library for custom setups. See:
[#4070](https://github.com/commercialhaskell/stack/issues/4070).
* With the new namespaced template feature, `stack templates` is no
longer able to meaningfully display a list of all templates
available. Instead, the command will download and display a
[help file](https://github.com/commercialhaskell/stack-templates/blob/master/STACK_HELP.md)
with more information on how to discover templates. See:
[#4039](https://github.com/commercialhaskell/stack/issues/4039)
* Build tools are now handled in a similar way to `cabal-install`. In
particular, for legacy `build-tools` fields, we use a hard-coded
list of build tools in place of looking up build tool packages in a
tool map. This both brings Stack's behavior closer into line with
`cabal-install`, avoids some bugs, and opens up some possible
optimizations/laziness. See:
[#4125](https://github.com/commercialhaskell/stack/issues/4125).
* Mustache templating is not applied to large files (over 50kb) to
avoid performance degredation. See:
[#4133](https://github.com/commercialhaskell/stack/issues/4133).
* `stack upload` signs the package by default, as documented. `--no-signature`
turns the signing off.
[#3739](https://github.com/commercialhaskell/stack/issues/3739)
* In case there is a network connectivity issue while trying to
download a template, stack will check whether that template had
been downloaded before. In that case, the cached version will be
used. See [#3850](https://github.com/commercialhaskell/stack/issues/3739).

Other enhancements:

* On Windows before Windows 10, --color=never is the default on terminals that
can support ANSI color codes in output only by emulation
* On Windows, recognise a 'mintty' (false) terminal as a terminal, by default
* `stack build` issues a warning when `base` is explicitly listed in
`extra-deps` of `stack.yaml`
* `stack build` suggests trying another GHC version should the build
plan end up requiring unattainable `base` version.
* A new sub command `run` has been introduced to build and run a
specified executable
similar to `cabal run`. If no executable is provided as the first argument, it
defaults to the first available executable in the project.
* `stack build` missing dependency suggestions (on failure to construct a valid
build plan because of missing deps) are now printed with their latest
cabal file revision hash. See
[#4068](https://github.com/commercialhaskell/stack/pull/4068).
* Added new `--tar-dir` option to `stack sdist`, that allows to copy
the resulting tarball to the specified directory.
* Introduced the `--interleaved-output` command line option and
`build.interleaved-output` config value which causes multiple concurrent
builds to dump to stderr at the same time with a `packagename> ` prefix. See
[#3225](https://github.com/commercialhaskell/stack/issues/3225).
* The default retry strategy has changed to exponential backoff.
This should help with
[#3510](https://github.com/commercialhaskell/stack/issues/3510).
* `stack new` now allows template names of the form `username/foo` to
download from a user other than `commercialstack` on Github, and can
be prefixed
with the service `github:`, `gitlab:`, or `bitbucket:`.
[#4039](https://github.com/commercialhaskell/stack/issues/4039)
* Switch to `githash` to include some unmerged bugfixes in `gitrev`
Suggestion to add `'allow-newer': true` now shows path to user config
file where this flag should be put into
[#3685](https://github.com/commercialhaskell/stack/issues/3685)
* `stack ghci` now asks which main target to load before doing the build,
rather than after
* Bump to hpack 0.29.0
* With GHC 8.4 and later, Haddock is given the `--quickjump` flag.
* It is possible to specify the Hackage base URL to upload packages to, instead
of the default of `https://hackage.haskell.org/`, by using `hackage-base-url`
configuration option.
* When using Nix, if a specific minor version of GHC is not requested, the
latest minor version in the given major branch will be used automatically.

Bug fixes:

* `stack ghci` now does not invalidate `.o` files on repeated runs,
meaning any modules compiled with `-fobject-code` will be cached
between ghci runs. See
[#4038](https://github.com/commercialhaskell/stack/pull/4038).
* `~/.stack/config.yaml` and `stack.yaml` terminating by newline
* The previous released caused a regression where some `stderr` from the
`ghc-pkg` command showed up in the terminal. This output is now silenced.
* A regression in recompilation checking introduced in v1.7.1 has been fixed.
See [#4001](https://github.com/commercialhaskell/stack/issues/4001)
* `stack ghci` on a package with internal libraries was erroneously looking
for a wrong package corresponding to the internal library and failing to
load any module. This has been fixed now and changes to the code in the
library and the sublibrary are properly tracked. See
[#3926](https://github.com/commercialhaskell/stack/issues/3926).
* For packages with internal libraries not depended upon, `stack build` used
to fail the build process since the internal library was not built but it
was tried to be registered. This is now fixed by always building internal
libraries. See
[#3996](https://github.com/commercialhaskell/stack/issues/3996).
* `--no-nix` was not respected under NixOS
* Fix a regression which might use a lot of RAM. See
[#4027](https://github.com/commercialhaskell/stack/issues/4027).
* Order of commandline arguments does not matter anymore.
See [#3959](https://github.com/commercialhaskell/stack/issues/3959)
* When prompting users about saving their Hackage credentials on upload,
flush to stdout before waiting for the response so the prompt actually
displays. Also fixes a similar issue with ghci target selection prompt.
* If `cabal` is not on PATH, running `stack solver` now prompts the user
to run `stack install cabal-install`
* `stack build` now succeeds in building packages which contain sublibraries
which are dependencies of executables, tests or benchmarks but not of the
main library. See
[#3787](https://github.com/commercialhaskell/stack/issues/3959).
* Sublibraries are now properly considered for coverage reports when the test
suite depends on the internal library. Before, stack was erroring when
trying to generate the coverage report, see
[#4105](https://github.com/commercialhaskell/stack/issues/4105).
* Sublibraries are now added to the precompiled cache and recovered from there
when the snapshot gets updated. Previously, updating the snapshot when there
was a package with a sublibrary in the snapshot resulted in broken builds.
This is now fixed, see
[#4071](https://github.com/commercialhaskell/stack/issues/4071).
* [#4114] Stack pretty prints error messages with proper `error` logging
level instead of `warning` now. This also fixes self-executing scripts
not piping plan construction errors from runhaskell to terminal (issue
#3942).
* Fix invalid "While building Setup.hs" when Cabal calls fail. See:
[#3934](https://github.com/commercialhaskell/stack/issues/3934)
* `stack upload` signs the package by default, as documented. `--no-signature`
turns the signing off.
[#3739](https://github.com/commercialhaskell/stack/issues/3739)