Also download OS-specific zip files while we're at it.
There are two files in `codeql-win64.zip` called `codeql/codeql` and
`codeql/codeql.exe`. Because of the order they were put into the zip,
they come out in the order `codeql/codeql.exe` followed by
`codeql/codeql`, and something on Windows thinks that the second file
has the same name as the first. It's because it's trying to emulate
linux and running `codeql/codeql` could run either one of them. We need
to make sure we definitely have the `.exe` file, so we explicitly
extract it again afterwards. This workaround is already used in some
other places. The order that the zip file is made in has now been fixed
so this shouldn't be a problem for future releases, so this workaround
can be removed in future.
Turns out gofmt doesn't actually return 1 when it finds problems, only when it finds source files which don't compile (all of which are now excluded).
This also fixes existing overlooked inconsistencies as a result of this mistake.
