Add --concurrently to solver-benchmarks

Make solver-benchmark use fresh cabal-dirs

Add nothunks test for parser

This way they won't remake caches on each run,
allowing to compare vastly different cabals.

Prohibit empty file paths.

Because there are plenty of `license-file: ""` and `data-dir: ""`,
out there, parser accepts and
filters out or transforms to "." respectively.

There are just two files which have non-empty filepath somewhere
else, namely in `hs-source-dirs:`. These are handler by `Quirks`.

Warning increase:

```diff
-40411 files contained warnings
+41163 files contained warnings
```

Rewrite cabal syntax file

Pr 6972 extra packages

Alex Biehl authored 4 years ago and Oleg Grenrus committed 4 years ago

The discussion in #6952 indicated that extra-packages stanzas wouldn't
quite work yet. It turns out in order for cabal to find exes for
already installed extra-packages we need to also consider `installed`
packages when pruning the install plan.

Includes some changes to OutputNormalizer

Resolve #7090: Remove v2-build beta note from --help

Nix style local builds have become the default

Resolve #7091: Require custom-setup for cabal-version: 1.24 and later

Add SPDX License list 3.10

Fix command notes being replaced by descriptions

This was causing the description of "new" prefixed and unprefixed
commands to be printed at both the top and bottom of their help text.

PR #6295: hsc2hs options

Simon Marlow authored 5 years ago and Oleg Grenrus committed 4 years ago

Motivation: I (simonmar) want to use hsc2hs with C++, which requires

```
hsc2hs-options: --cc=g++ --lflag=-lstdc++
```

We pass `hsc2hs-options` before or after `--cc` and `-lflag`,
depending on the version of `hsc2hs`.

I (phadej) added a tests:
- hsc2hs-options are passed to `hsc2hs` (but not to GHC e.g.).
- `--cc` has expected effect

`g++` tests doesn't seem to work on Windows, due mingw ncurses linkage
issue, https://github.com/msys2/MINGW-packages/issues/3531
We also need non-ancient hsc2hs (>= 0.68).

Bump Win32 bound to <2.11

Cabal is unaffected by the renamings done in 2.10.0.

Slightly more information on multiple package error

Partially addresses https://github.com/haskell/cabal/issues/6197

Pass -optcxx for GHC >= 8.10

Fixes https://github.com/haskell/cabal/issues/6421

To summarize, Cabal passes all C and C++ flags through GHC to the underlying C or C++ compiler using -optc. This works for GHC < 8.10, but now GHC expects C++ flags to come through -optcxx. This means that anything through -optc is ignored, so we cannot pass any flags to the C++ compiler. This change simply detects the GHC version and uses the correct arguments.

This PR has been tested manually and two PackageTests have been added to cabal-testsuite. They pass under GHC 8.8.4 and GHC 8.10.2.

Skip less: docker ulimit and local+noindex to run withRepo tests. 

This makes us skip one less test.
Also some small cleanups to test runner added.

Resolve #7061: v2-update updates file+noindex repository cache

Add skip reasons in cabal-testsuite

I introduced TestCode which allows to report more status information
than bare ExitCode.