x test mir-opt --bless tries to checkout src/llvm-project

[saethlin]

I tracked this down to this call, which tries to checkout the LLVM submodule, even if I have download-ci-llvm = true specifically because I do not want the submodule checked out:

rust/src/bootstrap/src/core/builder.rs

Line 1540 in 4428a05

if crate::core::build_steps::llvm::prebuilt_llvm_config(self, target).should_build() {

Here's my config, but I doubt it matters:

change-id = 999999

[llvm]
#assertions = false
download-ci-llvm = true

#[build]
#submodules = true

[rust]
codegen-backends = ["llvm"]
new-symbol-mangling = false
frame-pointers = true
deny-warnings = false
use-lld = true
incremental = false
debuginfo-level-std = 2
debuginfo-level = 1
debug = false
debug-logging = false