Subject: [PATCH] gnu: rust: fix building bootstrap chain

From: Ivan Petkov <[email-masked]>
Date: Mon, 17 Jun 2019 20:00:09 -0700

This patch fixes building rust versions 1.30 and onwards:

* Thanks to a newer GDB version being present, we no longer need to patch the
debug-info tests to the older (and now incorrect) format.
* Downgrade to llvm@6 for older compilers, which don't support the newer llvm@8.

—Ivan