Merge pull request #21771 from adrian-prantl/asan

Author: swift-ci

utils/build-script-impl

@@ -2524,6 +2524,14 @@ for host in "${ALL_HOSTS[@]}"; do
                                 -DLLDB_ALLOW_STATIC_BINDINGS=1
                                 -DLLDB_CODESIGN_IDENTITY=""
                             )
+
+                            if [[ "${ENABLE_ASAN}" ]] ; then
+                                # Limit the number of parallel tests.
+                                num_phys_cpu = $(sysctl hw.physicalcpu | cut -d : -f 2)
+                                cmake_options+=(
+                                    -DLLVM_LIT_ARGS="--threads=${num_phys_cpu}"
+                                )
+                            fi
                         fi
                         ;;
                 esac