fixup! Replace llvm-dev C++ stdlib with Xcode's in C++ test compilations
diff --git a/native/native.tests/tests/org/jetbrains/kotlin/konan/test/blackbox/support/util/Clang.kt b/native/native.tests/tests/org/jetbrains/kotlin/konan/test/blackbox/support/util/Clang.kt
index b6976f3..db75275 100644
--- a/native/native.tests/tests/org/jetbrains/kotlin/konan/test/blackbox/support/util/Clang.kt
+++ b/native/native.tests/tests/org/jetbrains/kotlin/konan/test/blackbox/support/util/Clang.kt
@@ -101,6 +101,10 @@
                 add("-Wno-#warnings")
                 // Workaround KT-69507
                 add("-D_LIBCPP_DISABLE_VISIBILITY_ANNOTATIONS")
+                // llvm 11 doesn't support "__attribute__((__using_if_exists__))", so we stub these manually
+                listOf("mbrtoc16", "c16rtomb", "mbrtoc32", "c32rtomb").forEach {
+                    add("-D$it=printf")
+                }
             }
         }
         addAll(additionalClangFlags)