Auto merge of rust-lang#112049 - Kobzol:pgo-omit-benchmarks, r=<try>

[do not merge] CI experiments

Various CI experiments for try/dist builds.

r? `@ghost`

compiler/rustc/Cargo.toml

@@ -23,7 +23,7 @@ stable_mir = { path = "../stable_mir" }
 [dependencies.tikv-jemalloc-sys]
 version = "0.6.0"
 optional = true
-features = ['unprefixed_malloc_on_supported_platforms']
+features = ['unprefixed_malloc_on_supported_platforms', 'background_threads']
 
 [features]
 # tidy-alphabetical-start

src/bootstrap/src/core/build_steps/compile.rs

@@ -1207,6 +1207,12 @@ pub fn rustc_cargo_env(
             rustc_llvm_env(builder, cargo, target)
         }
     }
+    if builder.config.jemalloc {
+        cargo.env(
+            "JEMALLOC_SYS_WITH_MALLOC_CONF",
+            "dirty_decay_ms:0,muzzy_decay_ms:0,abort_conf:true",
+        );
+    }
 }
 
 /// Pass down configuration from the LLVM build into the build of