From e03d3bee100bab4ac4cf6e093b507211987245eb Mon Sep 17 00:00:00 2001
From: Marko Vejnovic <marko@bun.com>
Date: Wed, 12 Nov 2025 14:40:12 -0800
Subject: [PATCH] ci(ENG-21502): Fix sccache not working inside Docker (#24597)

---
 .buildkite/Dockerfile | 14 ++++++++++++++
 scripts/bootstrap.sh  |  4 ++++
 2 files changed, 18 insertions(+)

diff --git a/.buildkite/Dockerfile b/.buildkite/Dockerfile
index 55e45ccdff..033aec633d 100644
--- a/.buildkite/Dockerfile
+++ b/.buildkite/Dockerfile
@@ -133,6 +133,20 @@ RUN ARCH=$(if [ "$TARGETARCH" = "arm64" ]; then echo "arm64"; else echo "amd64";
 
 RUN mkdir -p /var/cache/buildkite-agent /var/log/buildkite-agent /var/run/buildkite-agent /etc/buildkite-agent /var/lib/buildkite-agent/cache/bun
 
+# The following is necessary to configure buildkite to use a stable
+# checkout directory. sccache hashes absolute paths into its cache keys,
+# so if buildkite uses a different checkout path each time (which it does
+# by default), sccache will be useless.
+RUN mkdir -p -m 755 /var/lib/buildkite-agent/hooks && \
+    cat <<'EOF' > /var/lib/buildkite-agent/hooks/environment
+#!/bin/sh
+set -efu
+
+export BUILDKITE_BUILD_CHECKOUT_PATH=/var/lib/buildkite-agent/build
+EOF
+
+RUN chmod 744 /var/lib/buildkite-agent/hooks/environment
+
 COPY  ../*/agent.mjs /var/bun/scripts/
 
 ENV BUN_INSTALL_CACHE=/var/lib/buildkite-agent/cache/bun
diff --git a/scripts/bootstrap.sh b/scripts/bootstrap.sh
index ead3de99c8..7bc2a53ad6 100755
--- a/scripts/bootstrap.sh
+++ b/scripts/bootstrap.sh
@@ -1392,6 +1392,10 @@ create_buildkite_user() {
 		create_file "$file"
 	done
 
+	# The following is necessary to configure buildkite to use a stable
+	# checkout directory. sccache hashes absolute paths into its cache keys,
+	# so if buildkite uses a different checkout path each time (which it does
+	# by default), sccache will be useless.
 	local opts=$-
 	set -ef