[llvm_tools] automatically uprevs sys-devel/gcc whenever LLVM_NEXT is changed

BUG=b:192996912
TEST=update_chromeos_llvm_hash_unittest.py verified via CQ

Change-Id: Id06f054fdc4400c9b9af48c5383172192cb9a8a3
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/toolchain-utils/+/3021576
Tested-by: Christopher Di Bella <cjdb@google.com>
Auto-Submit: Christopher Di Bella <cjdb@google.com>
Reviewed-by: Luis Lozano <llozano@chromium.org>
Commit-Queue: Christopher Di Bella <cjdb@google.com>
1 file changed