ci(llvm): drop llvm-config from distribution; build + copy it by hand

CI confirmed what issue #364's analysis predicted: when LLVM_BUILD_TOOLS=Off,
cmake's `llvm_add_tool` never creates the `install-llvm-config` target
(both the `install(TARGETS)` call and `add_llvm_install_targets` are gated
on LLVM_BUILD_TOOLS in AddLLVM.cmake). LLVM_DISTRIBUTION_COMPONENTS errors
out at configure time with "Specified distribution component 'llvm-config'
doesn't have an install target".

Fix: drop `llvm-config` from the distribution whitelist, and after
`ninja install-distribution` completes, directly `ninja llvm-config`
(force-build the excluded-from-ALL target) and `fs_extra::file::copy` the
binary into the install prefix's `bin/` dir. Rust-side, co-located with
the rest of the Windows logic.

Still cleaner than the pre-rework YAML version:
- No YAML file round-trip for `--extra-args`
- No dead `LLVM_TOOL_LLVM_CONFIG_BUILD='On'` flag
- All Windows-specific logic in one Rust file, not split
- Uses install-distribution for everything that is distribution-aware
  (libs, headers, cmake-exports); only llvm-config takes the manual path

Author: nebasuke

solx-dev/src/llvm/platforms/shared.rs

@@ -172,21 +172,25 @@ pub fn shared_build_opts_coverage(enabled: bool) -> Vec<String> {
 /// never invokes any LLVM tool at runtime (it consumes LLVM as a library via
 /// inkwell), so linking them is pure waste. `LLVM_BUILD_TOOLS=Off` marks every
 /// tool `EXCLUDE_FROM_ALL`; `LLVM_INCLUDE_TOOLS=On` keeps `tools/` in the
-/// configure pass so the umbrella targets (`llvm-libraries`, `llvm-config`) are
-/// defined. `LLVM_DISTRIBUTION_COMPONENTS` whitelists the install set, which
+/// configure pass so the umbrella targets (`llvm-libraries` etc.) are defined.
+/// `LLVM_DISTRIBUTION_COMPONENTS` whitelists the install set, which
 /// `install-distribution` then honours — see #364.
 ///
-/// `llvm-config` is included because `llvm-sys` shells out to it at Rust build
-/// time to discover include paths and link flags. `lld-*` is always included
-/// because `shared_build_opts_projects` always enables `lld`. `mlir-*` is
-/// included only when `enable_mlir` is true.
+/// `llvm-config` is deliberately **not** in the distribution list: with
+/// `LLVM_BUILD_TOOLS=Off`, `llvm_add_tool` never creates the `install-llvm-config`
+/// cmake target (both `install(TARGETS)` and `add_llvm_install_targets` are
+/// gated on `LLVM_BUILD_TOOLS`), so referencing it here errors at configure
+/// time. `llvm-sys` still needs `llvm-config` at Rust build time — the Windows
+/// builder builds it via direct `ninja llvm-config` and copies the binary into
+/// the install prefix after `install-distribution` completes.
+/// `lld-*` is always included because `shared_build_opts_projects` always
+/// enables `lld`. `mlir-*` is included only when `enable_mlir` is true.
 ///
 pub fn windows_build_opts_distribution(enable_mlir: bool) -> Vec<String> {
     let mut components = vec![
         "llvm-libraries",
         "llvm-headers",
         "cmake-exports",
-        "llvm-config",
         "lld-libraries",
         "lld-headers",
         "lld-cmake-exports",

solx-dev/src/llvm/platforms/x86_64_windows_gnu.rs

@@ -78,6 +78,25 @@ pub fn build(
     // ~200 LLVM tool binaries solx doesn't use. See #364.
     crate::utils::ninja(llvm_build_final.as_ref(), "install-distribution")?;
 
+    // `llvm-config` is excluded from the distribution because LLVM_BUILD_TOOLS=Off
+    // prevents its install target from ever being defined. Build and copy it by
+    // hand so llvm-sys can find it at Rust build time.
+    crate::utils::command(
+        Command::new("ninja")
+            .arg("-C")
+            .arg(&*llvm_build_final_str)
+            .arg("llvm-config"),
+        "Building llvm-config",
+    )?;
+    let llvm_config_source = llvm_build_final.join("bin").join("llvm-config.exe");
+    let llvm_config_dest_dir = llvm_target_final.join("bin");
+    std::fs::create_dir_all(&llvm_config_dest_dir)?;
+    fs_extra::file::copy(
+        crate::utils::path_windows_to_unix(llvm_config_source)?,
+        crate::utils::path_windows_to_unix(llvm_config_dest_dir.join("llvm-config.exe"))?,
+        &fs_extra::file::CopyOptions::default(),
+    )?;
+
     let libstdcpp_source_path = match std::env::var("LIBSTDCPP_SOURCE_PATH") {
         Ok(libstdcpp_source_path) => PathBuf::from(libstdcpp_source_path),
         Err(error) => anyhow::bail!(