[llvm] [Github][RFC] Add workflow to diff codegen on llvm-test-suite (PR #190010)

[Luke Lau via llvm-commits]

================
@@ -0,0 +1,136 @@
+# When /test-suite is commented on a PR, checks out the PR, builds clang and
+# then the test-suite in several configurations. It then checks out the base of
+# the PR, builds clang and the test-suite again, and then uploads the diff of
+# the codegen.
+
+name: Diff test-suite codegen
+
+on:
+  issue_comment:
+    types:
+      - created
+
+jobs:
+  test-suite:
+    name: Build and diff
+    runs-on: ubuntu-24.04
----------------
lukel97 wrote:

Wow the build is almost twice as fast. The only issue is that it looks like the cross compile builds are failing because the version of CMake is too old. It looks like it's version 3.28 on the image but we need at least 3.29 since the toolchain files use [CMAKE_LINKER_TYPE](https://cmake.org/cmake/help/latest/variable/CMAKE_LINKER_TYPE.html). The default github ubuntu runner has 3.31: https://github.com/actions/runner-images/blob/main/images/ubuntu/Ubuntu2404-Readme.md#tools. 

Are you able to update the CMake version in the image or should we try and install a newer version in this workflow?

https://github.com/llvm/llvm-project/pull/190010