[compiler-rt][nfc] DenseMap needs placement new (#133329)

Author: mtrofin

compiler-rt/lib/sanitizer_common/sanitizer_dense_map.h

@@ -19,6 +19,9 @@
 #include "sanitizer_common.h"
 #include "sanitizer_dense_map_info.h"
 #include "sanitizer_internal_defs.h"
+// Placement-new is needed for bucket allocation. This avoids needing to include
+// it everywhere we use DenseMap.
+#include "sanitizer_placement_new.h"
 #include "sanitizer_type_traits.h"
 
 namespace __sanitizer {