fix(IDX): don't cache jemalloc build (#5174)

This prevents `jemalloc` from being cached. An issue in the build
currently causes the cache to get polluted, which makes all subsequent
CI runs to fail the build determinism tests.

The root cause is not yet 100% clear.

Author: nmattia

.github/actions/bazel-test-all/action.yaml

@@ -77,6 +77,18 @@ runs:
               bazel_targets+=( "$tgt" )
             done
 
+            # jemalloc -- or rather, the "hermetic" zig toolchain -- has issues when too
+            # many targets are built concurrently (leads to determinism issues & linking
+            # errors).
+            #
+            # To work around this, we build jemalloc separately.
+            if [ $(uname -o) != "Darwin" ]; then
+              if [[ $release_build == "true" ]]; then
+                bazel build "${bazel_args[@]}" @@jemalloc//:libjemalloc --config=release
+              else
+                bazel build "${bazel_args[@]}" @@jemalloc//:libjemalloc
+              fi
+            fi
 
             if [[ $diff_only == "true" ]]; then
                 target_pattern_file=$(mktemp)

third_party/jemalloc/BUILD.jemalloc.bazel

@@ -50,6 +50,13 @@ configure_make(
     # Specify the name for the static archive instead of defaulting to <rulename>.a
     out_static_libs = ["libjemalloc.a"],
 
+    # The jemalloc build (most likely rules_foreign_cc) sometimes creates corrupt artifacts
+    # which can pollute the cache -- so we build it locally.
+    tags = [
+        "manual",
+        "no-cache",
+    ],
+
     # Ensures only the static archive is built. Otherwise (make) targets (including jemalloc.sh) cause
     # non-determinism in the build and aren't necessary for us.
     targets = [