Rollup merge of #154441 - ZuseZ4:macos-bootstrap-stamp, r=Kobzol

bootstrap: force a CI LLVM stamp bump

To see if this helps with #154408

r? @Kobzol

Author: jhpratt

src/bootstrap/download-ci-llvm-stamp

@@ -1,4 +1,4 @@
 Change this file to make users of the `download-ci-llvm` configuration download
 a new version of LLVM from CI, even if the LLVM submodule hasn’t changed.
 
-Last change is for: https://github.com/rust-lang/rust/pull/153179
+Last change is for: https://github.com/rust-lang/rust/pull/151063