[llvm] [CI] Save sccache logs (PR #155444)

[Aiden Grossman via llvm-commits]

https://github.com/boomanaiden154 created https://github.com/llvm/llvm-project/pull/155444

This patch saves the sccache logs to the artifacts. If sccache dies and the server prints logs, we currently do not collect them anywhere and they do not get dumped to STDOUT/STDERR. If the process is directly getting killed (SIGTERM), it seems like it doesn't dump anything, but in most other cases we should be able to see something.

Related to #155442.

>From 0189015150062599b94d5282f708422e8fca9d6e Mon Sep 17 00:00:00 2001
From: Aiden Grossman <aidengrossman at google.com>
Date: Tue, 26 Aug 2025 16:11:48 +0000
Subject: [PATCH] [CI] Save sccache logs

This patch saves the sccache logs to the artifacts. If sccache dies and
the server prints logs, we currently do not collect them anywhere and
they do not get dumped to STDOUT/STDERR. If the process is directly
getting killed (SIGTERM), it seems like it doesn't dump anything, but in
most other cases we should be able to see something.

Related to #155442.
---
 .github/workflows/premerge.yaml | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/.github/workflows/premerge.yaml b/.github/workflows/premerge.yaml
index 9d925517a7211..2b43f462dc140 100644
--- a/.github/workflows/premerge.yaml
+++ b/.github/workflows/premerge.yaml
@@ -65,7 +65,7 @@ jobs:
           # several test suites in a row and discard statistics that we want
           # to save in the end.
           export SCCACHE_IDLE_TIMEOUT=0
-          sccache --start-server
+          SCCACHE_LOG=info SCCACHE_ERROR_LOG=artifacts/sccache.log sccache --start-server
 
           ./.ci/monolithic-linux.sh "${projects_to_build}" "${project_check_targets}" "${runtimes_to_build}" "${runtimes_check_targets}" "${runtimes_check_targets_needs_reconfig}" "${enable_cir}"
       - name: Upload Artifacts
@@ -117,7 +117,7 @@ jobs:
           call C:\\BuildTools\\Common7\\Tools\\VsDevCmd.bat -arch=amd64 -host_arch=amd64
           # See the comments above in the Linux job for why we define each of
           # these environment variables.
-          bash -c "export SCCACHE_GCS_BUCKET=$CACHE_GCS_BUCKET; export SCCACHE_GCS_RW_MODE=READ_WRITE; export SCCACHE_IDLE_TIMEOUT=0; sccache --start-server; .ci/monolithic-windows.sh \"${{ steps.vars.outputs.windows-projects }}\" \"${{ steps.vars.outputs.windows-check-targets }}\""
+          bash -c "export SCCACHE_GCS_BUCKET=$CACHE_GCS_BUCKET; export SCCACHE_GCS_RW_MODE=READ_WRITE; export SCCACHE_IDLE_TIMEOUT=0; SCCACHE_LOG=info SCCACHE_ERROR_LOG=artifacts/sccache.log sccache --start-server; .ci/monolithic-windows.sh \"${{ steps.vars.outputs.windows-projects }}\" \"${{ steps.vars.outputs.windows-check-targets }}\""
       - name: Upload Artifacts
         # In some cases, Github will fail to upload the artifact. We want to
         # continue anyways as a failed artifact upload is an infra failure, not