Simplify TSAN build CI; use in-source build

Author: tkf

.buildkite/pipelines/main/misc/sanitizers.yml

@@ -42,5 +42,6 @@ steps:
     if: | # We only run the `tsan` job on Julia 1.8 and later.
       (pipeline.slug != "julia-release-1-dot-6") && (pipeline.slug != "julia-release-1-dot-7")
     commands: |
-      echo "--- Build julia-debug runtime with TSAN"
-      contrib/tsan/build.sh ./tmp/test-tsan -j$${JULIA_CPU_THREADS:?} -C src debug
+      echo "--- Build julia binary with TSAN"
+      cp contrib/tsan/Make.user.tsan Make.user
+      make -C src -j$${JULIA_CPU_THREADS:?} debug