[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>
diff --git a/llvm_tools/update_chromeos_llvm_hash.py b/llvm_tools/update_chromeos_llvm_hash.py
index afc63f3..c54087b 100755
--- a/llvm_tools/update_chromeos_llvm_hash.py
+++ b/llvm_tools/update_chromeos_llvm_hash.py
@@ -483,6 +483,11 @@
   # Determines whether to print the result of each executed command.
   llvm_patch_management.verbose = verbose
 
+  # Unconditionally update sys-devel/gcc
+  sys_devel_gcc = 'sys-devel/gcc'
+  if sys_devel_gcc not in packages:
+    packages.append(sys_devel_gcc)
+
   # Construct a dictionary where the key is the absolute path of the symlink to
   # the package and the value is the absolute path to the ebuild of the package.
   paths_dict = CreatePathDictionaryFromPackages(chroot_path, packages)