stack exec -- pacman broken

[Shayne Fletcher]

this isn't exactly a GHC issue but perhaps someone knows how to get it
resolved? (suspecting commercial/stack i've raised [this issue](
https://github.com/commercialhaskell/stack/issues/5732) there).

tl;dr `stack exec -- pacman -S ...` like commands required for building GHC
on windows are broken and have been for sometime

ghc-lib CI runs this command on windows,
```
stack --resolver lts-18.23   exec -- pacman -S autoconf automake-wrapper
make patch python tar mintty --noconfirm
```
this normally works ok but as of today,
```
warning: database file for 'clang32' does not exist (use '-Sy' to download)
warning: mintty-1~3.6.0-1 is up to date -- reinstalling
error: failed to prepare transaction (could not find database)
```

in another project (ghc-lib-parser-ex), a similar command (different
compiler version/stack yaml) has been producing the following reliably long
enough that i'm sorry to say i just gave up testing it windows.
```
:: File /var/cache/pacman/pkg/automake1.9-1.9.6-3-any.pkg.tar.zst is
corrupted (invalid or corrupted package (PGP signature)).
Do you want to delete it? [Y/n]
error: automake1.10: signature from "David Macek <david.macek.0 at gmail.com>"
is unknown trust
error: automake1.11: signature from "David Macek <david.macek.0 at gmail.com>"
is unknown trust
error: automake1.12: signature from "David Macek <david.macek.0 at gmail.com>"
is unknown trust
error: automake1.13: signature from "David Macek <david.macek.0 at gmail.com>"
is unknown trust
error: automake1.14: signature from "David Macek <david.macek.0 at gmail.com>"
is unknown trust
error: automake1.15: signature from "David Macek <david.macek.0 at gmail.com>"
is unknown trust
:: File /var/cache/pacman/pkg/automake1.10-1.10.3-4-any.pkg.tar.zst is
corrupted (invalid or corrupted package (PGP signature)).
Do you want to delete it? [Y/n]
:: File /var/cache/pacman/pkg/automake1.11-1.11.6-4-any.pkg.tar.zst is
corrupted (invalid or corrupted package (PGP signature)).
Do you want to delete it? [Y/n]
:: File /var/cache/pacman/pkg/automake1.12-1.12.6-4-any.pkg.tar.zst is
corrupted (invalid or corrupted package (PGP signature)).
Do you want to delete it? [Y/n]
:: File /var/cache/pacman/pkg/automake1.13-1.13.4-5-any.pkg.tar.zst is
corrupted (invalid or corrupted package (PGP signature)).
Do you want to delete it? [Y/n]
:: File /var/cache/pacman/pkg/automake1.14-1.14.1-4-any.pkg.tar.zst is
corrupted (invalid or corrupted package (PGP signature)).
Do you want to delete it? [Y/n]
error: automake1.16: signature from "David Macek <david.macek.0 at gmail.com>"
is unknown trust
error: failed to commit transaction (invalid or corrupted package)
:: File /var/cache/pacman/pkg/automake1.15-1.15.1-2-any.pkg.tar.zst is
corrupted (invalid or corrupted package (PGP signature)).
Do you want to delete it? [Y/n]
:: File /var/cache/pacman/pkg/automake1.16-1.16.3-1-any.pkg.tar.zst is
corrupted (invalid or corrupted package (PGP signature)).
Do you want to delete it? [Y/n]
Errors occurred, no packages were upgraded.
```

-- 
Shayne Fletcher
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