Auto merge of #95440 - jyn514:error-index, r=Mark-Simulacrum

Fix `x test src/tools/error_index_generator --stage {0,1}`

There were two fixes needed:
1. Use `top_stage` instead of `top_stage - 1`. There was a long and torturous comment about trying to match rustdoc's version, but it works better without the hard-coding than with (before it gave errors that `libtest.so` couldn't be found).
2. Make sure that `ci-llvm/lib` is added to LD_LIBRARY_PATH. Previously the error index would be unable to load LLVM for stage0 builds.

At some point we should probably have a discussion about how rustdoc stages should be numbered;
confusion between 0/1/2 has come up several times in bootstrap now. cc https://github.com/rust-lang/rust/issues/92538

Note that this is still broken when using `download-rustc = true` and `--stage 1`,
but that's *really* a corner case and should affect almost no one. `--stage {0,2}`
work fine with download-rustc.

Fixes https://github.com/rust-lang/rust/issues/80096.

1 files changed, 13 insertions, 9 deletions

diff --git a/src/bootstrap/builder.rs b/src/bootstrap/builder.rs
index e816f9b4c07..8c06a007013 100644
--- a/src/bootstrap/builder.rs
+++ b/src/bootstrap/builder.rs
@@ -835,6 +835,18 @@ impl<'a> Builder<'a> {
         }
     }
 
+    pub fn rustc_lib_paths(&self, compiler: Compiler) -> Vec<PathBuf> {
+        let mut dylib_dirs = vec![self.rustc_libdir(compiler)];
+
+        // Ensure that the downloaded LLVM libraries can be found.
+        if self.config.llvm_from_ci {
+            let ci_llvm_lib = self.out.join(&*compiler.host.triple).join("ci-llvm").join("lib");
+            dylib_dirs.push(ci_llvm_lib);
+        }
+
+        dylib_dirs
+    }
+
     /// Adds the compiler's directory of dynamic libraries to `cmd`'s dynamic
     /// library lookup path.
     pub fn add_rustc_lib_path(&self, compiler: Compiler, cmd: &mut Command) {
@@ -845,15 +857,7 @@ impl<'a> Builder<'a> {
             return;
         }
 
-        let mut dylib_dirs = vec![self.rustc_libdir(compiler)];
-
-        // Ensure that the downloaded LLVM libraries can be found.
-        if self.config.llvm_from_ci {
-            let ci_llvm_lib = self.out.join(&*compiler.host.triple).join("ci-llvm").join("lib");
-            dylib_dirs.push(ci_llvm_lib);
-        }
-
-        add_dylib_path(dylib_dirs, cmd);
+        add_dylib_path(self.rustc_lib_paths(compiler), cmd);
     }
 
     /// Gets a path to the compiler specified.