Build LLVM for Windows (#248)

This PR changes the CI build scripts to also build LLVM for windows.
**It doesn't build `revive` itself for windows**. This will come in a
follow up. But once we have a LLVM binary release the turn around time
will be much quicker for experimenting with the revive windows build.

I manually uploaded the release those changes produce
[here](https://github.com/paritytech/revive-alex-workflowtest/releases/tag/llvm-18.1.8-revive.22f3ceb).
This enables this PR's CI to find the proper release. This is necessary
because I am also making changes to the folder structure and artifact
naming that the other CI jobs are depending on.

Releases generated from this branch can be inspected here:
https://github.com/paritytech/revive-alex-workflowtest/releases/tag/v0.1.0-dev.12

Summary of changes:
- Change `llvm-builder` to use MSVC toolchain on windows
- Fix `llvm-builder` to work with `.exe` files
- Unify the llvm release jobs into a single one. This removed a lot of
copy pasted code and also speeds up the build by giving each their own
runner.
- Use the LLVM target triple to name the binary releases instead of an
ad-hoc naming convention
- Remove the nested folder hierarchy inside the llvm release. Its just
now a single folder `llvm-<target>` that contains the toolchain.
- Give jobs and workflows consistent names
- Replace all runners bei their `*-latest` counterpart
- Only use `parity-large` to build llvm now. All other jobs use github
runners

crates/llvm-builder/src/utils.rs

@@ -7,6 +7,7 @@ use std::process::Command;
 use std::process::Stdio;
 use std::time::Duration;
 
+use anyhow::Context;
 use path_slash::PathBufExt;
 
 /// The LLVM host repository URL.
@@ -131,11 +132,8 @@ pub fn path_windows_to_unix<P: AsRef<Path> + PathBufExt>(path: P) -> anyhow::Res
 
 /// Checks if the tool exists in the system.
 pub fn check_presence(name: &str) -> anyhow::Result<()> {
-    let description = &format!("checking the `{name}` executable");
-    log::info!("{description}");
-
-    command(Command::new("which").arg(name), description)
-        .map_err(|_| anyhow::anyhow!("Tool `{}` is missing. Please install", name))
+    which::which(name).with_context(|| format!("Tool `{name}` is missing. Please install"))?;
+    Ok(())
 }
 
 /// Identify XCode version using `pkgutil`.